You can fit anything anywhere with a big enough hammer and a torch, but with all the cheap stroker kits and great heads available for small blocks and the ability to make as much power (and more) with less engine weight for the same $$$, who would want all the grief of trying to shoehorn a big block into an old 60's A body? You've already got enough to do just upgrading the brakes so you don't rear end the first idiot with a new car with 4 wheel power disc brakes that cuts in front of you and decides to stop. Then there's the spindly little rear that has to be replaced and of course the restoration of the body and interior. Good luck with all that, cause it's a massive undertaking.