When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Only heads that are decent that can be used are are 351C 4v heads... good luck finding a set of those. Other than that youre stuck with aftermarket.
This is what i had done on my 400. GOOD valve job, mild port work, milled .040" (iirc) , energizer cam, headers, edeljunk intake and carb. After that it was "bearable", however someone dosed it with some sand would be my guess and spun a main. Dropped in the diesel and havent looked back.