You could just go find some closed chamber 516 or the even better 915 head if you're looking to keep your project cheap. You would need to put a bit more $$$ into the 516s but they can be made to work.

I have 396/430 hp/tq with a set on my 383. I had much less with the vaunted boat anchor 906's on there before for the exact reasons posted above.

let the magazine guys have the 906's and other open chamber heads. If you want compression and quench closed chamber is the only way to go...IMHO