There are several versions of the FRPP aluminum heads. THe GT40Y303's flow about like a set of GT40P's - a bit better, but not much. The GT40X heads flow about like the standard TFS or Edelbrock heads. Both sets have 1.94" intakes/1.54" exhaust valves. Both are intake biased in their flows (intake side flows better than exhaust side) so they respond well to split duration cams with more exhaust lift/duration. They also recently came out with the "Z" head, which flows more like the better flowing AFR 165/185 units.
So, which ones were you speaking of? I have the Y heads -- I wanted my motor to perform a little better than stock, but I didn't want to lose any bottom end. And I wanted to knock 50lbs. of weight off the front - so the Y heads were perfect for me. Love 'em.
If you're trying to build big peak power numbers - you'll want more head than the Y's.