The 62's. They have open chambers and don't need as much timing to make decent power.
Be careful though, both have relatively small chambers and on an otherwise "stock" 400 build will result in a compression ratio that's too high for pump gas.
Tell us more about what you're planning to do?
I'm not sure if you followed the other threads, but I have a '75 400 in need of a rebuild (557 block casting). Factory specs are either 170 or 185 hp; I have not pulled any more numbers off the block yet to see what it came out of. I know I can NOT do a high performance build on this block due to thin web castings but everything I read says you can go up to 400 hp.
So, my plans....
No stroker for this one; just a standard crank.
A mild cam and a bigger exhaust (2 1/2" with x-pipe).
I was thinking these heads would help it breathe better but it appears the'll just raise compression. The current heads should have 101 cc chambers but still have big valves. Dished pistons would allow me to use the 62' but would there be any benefit? Save my money and just buy domed pistons to increase compression on the existing heads? There is 0.11" difference in size on the intake valve between my heads and the 62's. Will it make that much of a difference?
I've made no decision yet about an intake. Thoughts?
MSD distributor, electronic ignition. Anyone have opinions on mechanical advance vs vacuum advance?
Muncie 4 speed (m-20 or 21).
Dark blue paint, blue interior.
Power steering, power brakes, a/c (factory a/c car, a necessary evil living in Florida).