I want to put a new exhaust system on my 70 Challenger 383 with auto transmission. I want to get a set of manifolds taht are correct for a challenger. It currently has casting number 2843992/2806900 which are not correct. From what I have been able to gather, it should have 2951865/2899879 but these seem to be harder to find and more expensive. I appears that 3751068/3751071 will also work and these are easier to find and cheaper. I don't require date/numbers matching. What is the physical difference between the two sets? Is it a difference in clocking of the mounting bolts? Any help would be appreciated.

Thanks,

Michael