As for those Stealth heads not supporting 500 inches, well, I heartily disagree. They will support them just fine, just at a lower rpm. I have run 535 cubes with 906 heads, so I have some experience with this. A stealth headed 451 will peak torque about 4500 rpm with the right parts, a 512 with the same heads 3900 rpm. The 451 will want more rpm, say up to 6,000 with a street/strip cam. The 512 would be making the same power by 5300 rpm. Which one do you think will pull hardest with a street gear?