WIW X-Heads

JBurch said
X heads are an open chamber head; to achieve your goal of 400 to 430hp is gonna require port work, not a lot but some.

Go back in the "Mopar Muscle" archives about 12 to 14 years, Dulitch built a 360, he ported the heads (587 castings I think), with a Comp Magnum 280 cam he dynoed out around 430hp; in the zone you hope to be. It would be good reference materiel to help you get where you want to go.

What ever you do, good luck.

Here's the article:

http://www.moparmusclemagazine.com/techarticles/engine/mopp_0211_340_x_head_buildup/viewall.html

This ^^^ is why I kept my iron heads and reworked them over. machine work expense has been kept to a minimum due to a colleague having a seat and guide machine but I still had to send out to be resurfaced. total machine work $200, total in springs, retainers, keepers, guides, seat inserts, and valves: $500. I got a lot of good deals on new stuff here on the forum and surprisingly, Rockauto.