The first cut is always the deepest...
I noticed you said "get it cut", which makes me think you might be planning on taking it somewhere and paying them to do the work of cutting it. I don't know how much such a task would cost at your average automotive shop, but I am guessing it would cost more than the actual task was worth.
$100, $150, $200? I don't know, but I doubt any place would agree to do it if they weren't able to get at least that much out of the job (otherwise it would cost more to pay the guy to do it than what they were getting from you).
Given that they would likely pull the piece off the car before cutting it is going to cost ya.
Reinstalling it? Sure, but it'll cost ya.
If you have no tools, no room, or little to no confidence in your mechanical abilities, then I would advise against trying to cut it yourself. But if you have the tools (a rotary tool/dremmel is all you need really), the room (a garage and some jack-stands), and any mechanical inclination at all (change your own oil? you're good!), then you can most likely do the cutting yourself and be just fine.
The easiest route is just buy the valance from somewhere (like @A Guy pointed out above) and swap it out yourself, but that does involve some extra work since removing and reinstalling that piece is mildly labor/time intensive if you've never done something like that before. It can be done surely, but honestly I would say why not try the cutting yourself with the knowledge that if you mess that up somehow, you can always go to option B of swapping it out with a new one that's already notched.
If you want to attempt it yourself, I would suggest grabbing one of the Dremmel knock-offs from Harbor Freight to do the cutting. It's got enough torque to do the job without getting bogged down like their cheaper rotary tools will, but it's inexpensive enough not to make it a bad idea to buy it for this one time use (and honestly, you'll get more use out of it once you have it at your disposal).
The little dark-red cut-off wheels that come with those tools will cut the plastic on the valance, but they tend to become less effective at cutting pretty quickly, so you'll use up the 3 that come with the tool before you get done cutting both sides unless you're really careful. Personally, I like to leave myself with plenty of room for error, so I bought an extra 10 pack of those cut-off wheels to do my job, but I got them from Home Depot to eliminate any question about the quality of the discs (which I would be suspect of if buying them from Harbor Freight).
Other than that, you would need a couple of jack stands to hoist the rear end of the car up onto so you have room to roll around under there to get at the right angle to do the cutting from each side/front or back. And you will also need some masking tape or painters tape to tape off your cut lines once you have them decided upon**.
And that's it for the tool list if you want to DIY. Throw a little patience and a lot of time, and you're good to go!
Good luck with it,
Nuke
** - Oddly enough I found the hardest part of the whole job was to figure out how/where to lay my cut lines on the valance so that both sides would look even and identical - in other words, I didn't want it to look like I had cut them out. There's no measurements online (that I could find) that tell you where the cut lines are supposed to be in relation to the other lines on the car's rear end. I gathered up a bunch of pictures of the rear end of other Challengers with dual exhaust, both from far away and up close, and then just studied over them to visually pick out which body panel lines I could trust to be a set distance away from where I wanted to cut. Things like the license plate cut-out and rear tail-light plastic assembly's break line between the trunk lid and the rear quarter panel were prominent landmarks. The vertical lines of the cuts in relation to the vertical lines of the inside of the rear tires was another landmark I used.
Once I thought I had a good idea how to tape off the cut-lines, I actually went and did just that, then put the car out in the driveway and stared at its rear end for a while. Up close, far away, from the left, from the right...if anything didn't look lined up, it got re-measured and re-taped. There was some trial and effort there for sure, but I knew having either side's exhaust port even slight askew would bother me to no end. So I endured it until I thought I was ready to go. The key is to come up with a set of measurements that can be used to lay the tape one side and then reused exactly to lay the tape on the other side. Once you have that, you know they are going to be symmetrical and unlikely to look like they weren't there all along.
Making the cuts isn't all that hard. You just have to be very patient and conscientiously aware of your subconscious desire to hurry through the task and move too quickly. Keeping the cutting wheel from going too far in or meandering off your cut lines takes concentration, but it can surely be done if the beers are kept to a minimum. Also, realizing that you can always cut more off but never put any back, I found it was good to make my tape lines slightly inboard from where the true lines should end up (like 2 millimeters inboard). That way any slight mistakes where I veered off the cut lines could be fixed without trashing the whole deal and replacing the valance with another one.
I was about to pipe up and mention the deal about needing to either swap out the rear plastic valance or cut it to allow for dual exhaust exits, but then I saw this, so you're already aware of the need for one more step before taking it for the exhaust.
I noticed you said "get it cut", which makes me think you might be planning on taking it somewhere and paying them to do the work of cutting it. I don't know how much such a task would cost at your average automotive shop, but I am guessing it would cost more than the actual task was worth.
$100, $150, $200? I don't know, but I doubt any place would agree to do it if they weren't able to get at least that much out of the job (otherwise it would cost more to pay the guy to do it than what they were getting from you).
Given that they would likely pull the piece off the car before cutting it is going to cost ya.
Reinstalling it? Sure, but it'll cost ya.
If you have no tools, no room, or little to no confidence in your mechanical abilities, then I would advise against trying to cut it yourself. But if you have the tools (a rotary tool/dremmel is all you need really), the room (a garage and some jack-stands), and any mechanical inclination at all (change your own oil? you're good!), then you can most likely do the cutting yourself and be just fine.
The easiest route is just buy the valance from somewhere (like @A Guy pointed out above) and swap it out yourself, but that does involve some extra work since removing and reinstalling that piece is mildly labor/time intensive if you've never done something like that before. It can be done surely, but honestly I would say why not try the cutting yourself with the knowledge that if you mess that up somehow, you can always go to option B of swapping it out with a new one that's already notched.
If you want to attempt it yourself, I would suggest grabbing one of the Dremmel knock-offs from Harbor Freight to do the cutting. It's got enough torque to do the job without getting bogged down like their cheaper rotary tools will, but it's inexpensive enough not to make it a bad idea to buy it for this one time use (and honestly, you'll get more use out of it once you have it at your disposal).
The little dark-red cut-off wheels that come with those tools will cut the plastic on the valance, but they tend to become less effective at cutting pretty quickly, so you'll use up the 3 that come with the tool before you get done cutting both sides unless you're really careful. Personally, I like to leave myself with plenty of room for error, so I bought an extra 10 pack of those cut-off wheels to do my job, but I got them from Home Depot to eliminate any question about the quality of the discs (which I would be suspect of if buying them from Harbor Freight).
Other than that, you would need a couple of jack stands to hoist the rear end of the car up onto so you have room to roll around under there to get at the right angle to do the cutting from each side/front or back. And you will also need some masking tape or painters tape to tape off your cut lines once you have them decided upon**.
And that's it for the tool list if you want to DIY. Throw a little patience and a lot of time, and you're good to go!
Good luck with it,
Nuke
** - Oddly enough I found the hardest part of the whole job was to figure out how/where to lay my cut lines on the valance so that both sides would look even and identical - in other words, I didn't want it to look like I had cut them out. There's no measurements online (that I could find) that tell you where the cut lines are supposed to be in relation to the other lines on the car's rear end. I gathered up a bunch of pictures of the rear end of other Challengers with dual exhaust, both from far away and up close, and then just studied over them to visually pick out which body panel lines I could trust to be a set distance away from where I wanted to cut. Things like the license plate cut-out and rear tail-light plastic assembly's break line between the trunk lid and the rear quarter panel were prominent landmarks. The vertical lines of the cuts in relation to the vertical lines of the inside of the rear tires was another landmark I used.
Once I thought I had a good idea how to tape off the cut-lines, I actually went and did just that, then put the car out in the driveway and stared at its rear end for a while. Up close, far away, from the left, from the right...if anything didn't look lined up, it got re-measured and re-taped. There was some trial and effort there for sure, but I knew having either side's exhaust port even slight askew would bother me to no end. So I endured it until I thought I was ready to go. The key is to come up with a set of measurements that can be used to lay the tape one side and then reused exactly to lay the tape on the other side. Once you have that, you know they are going to be symmetrical and unlikely to look like they weren't there all along.
Making the cuts isn't all that hard. You just have to be very patient and conscientiously aware of your subconscious desire to hurry through the task and move too quickly. Keeping the cutting wheel from going too far in or meandering off your cut lines takes concentration, but it can surely be done if the beers are kept to a minimum. Also, realizing that you can always cut more off but never put any back, I found it was good to make my tape lines slightly inboard from where the true lines should end up (like 2 millimeters inboard). That way any slight mistakes where I veered off the cut lines could be fixed without trashing the whole deal and replacing the valance with another one.
