Pro Comp heads are junk. Ported D3VE heads will be as good or better.

I did a low buck 460 build for my truck a while back that I am quite happy with. KB137 pistons, ported E6TE (D3VE) heads (exhaust only), Edelbrock Performer intake, Holley 750 DP carb., Comp CL34-235-4. This build is in the ballpark of 400 HP and was quite affordable.

A similar build with more cam duration, ported intake side of heads, Performer RPM or Weiand Stealth should get in the 450+ HP range.