Josh you posted this under the Fe big block Ford thread. I would look into asking the same question under the 429-460 thread where Paul Kane will hopefully see it and respond. He works with these engine for a living .To quickly answer your question about your 429 yes with DOVE-C heads you should be able to get 400 h.p. pretty easily. The problems like Tech has said is in the compression rations with the low profile heads, running on pump gas. Mine has slightly dished pistons made by Keith Black and my compression is around 9.9. Ask Paul, he will steer you right and you can read my thread where he has chimmed in with advice. Good to see another big block Ford guy here.
http://www.clubhotrod.com/forums/showthread.php?t=38755