[jonmandude]

It depends on your desires. Do you want a "correct" restoration or are you building a car to drive that is also a 72 Challenger?

If you are trying to restore the car correct as possible, you should look for a date coded block......good luck.

If you are trying to restore the car for your enjoyment, something to drive around on the weekends, get a crate engine. or go the "resto-mod" route and go bigger. It doesn't matter when the original engine is already gone, and even with the original it doesn't matter that much with a small block.

my two cents.