I am having a very difficult time trying to successfully install an original (build date of 12/1969) cast iron Six Pack intake manifold onto my 440 cu in engine. My car is a 1970 Dodge Challenger R/T and it originally was a Six Pack car. However, over the years (I have owned the car since 7/1971), I sold the original six pack setup and used other various intake setups. Quite a few years ago, I had a reputable engine builder rebuild my 440 for me and after getting the engine back from the builder, I installed a complete Six Pack setup again, but this time I utilized an aluminum intake manifold. I was very glad to be utilizing a Six Pack setup again. But now I am at the point of trying to replace the aluminum intake with an original cast iron Six Pack intake manifold as I first stated above. I have uninstalled and reinstalled the cast iron Six Pack intake manifold 3 times now and I can't seem to eliminate a vacuum leak. I went back to the paperwork that I received from the builder who professionally rebuilt my 440 and it shows that he 'resurfaced' the heads .010 of an inch. If I am trying to install an original cast iron Six Pack intake manifold, would it make sense that the head mating surfaces would need to be 'resurfaced' by .010 of an inch also? I just can't figure out what else might be causing my vacuum leak. Any suggestions?