I wiped out a flat tappet cam in my 302 a while back, probably due to improper break in and low/no zinc oil, and decided to use a stock H.O. cam with retrofit roller lifters. The timing chain had a lot more play in it that I would have expected with only a few thousand miles on it, so I want to replace that too, but Im not sure which one I need. Do I go with the 84 and up timing chain to go with the cam, or the pre 84 to go with the 78 block? Im not sure off hand what the difference is. For what its worth, its getting a conversion to EFI at the same time, so mounting a fuel pump eccentric is not a concern (ran into that problem just recently on a 460).