440 head numbers

You'll never feel the difference in 915, 346 or 452s. Never. Not a single narry bit. The best would be the 452 because if the seats are in grindable condition, they are already hardened. with everything equal, they all flow the same. You'll get yahoos sayin "but the 915s are better, blah, blah, blah...", but the FACT is that your butt dyno will never know the difference. In fact, the 452s beat out the 915s in several peaks on the RPM graph. But the differences are all so slight, that you can say they all flow the SAME.