But you could experience lower compression if you use large combustion chamber 460 heads with a 429 block and crank and you could also get tons of compression if you use 429 heads on a 460 because of the difference in stroke.
Nope, the 429 and 460 are same block. The 390 is a Y-Block. Two different family of engines. Got to love ford for having a different engine for every different application. At least on a Chevrolet for the most part a small block is a small block and a big block is a big block. I mean for god sakes ford has 3 different 351's and they are all different.