Even though I run 440-1 heads, I have seen so many motors with B1 stuff make more power I recommend them on anything 499 and bigger as long as you are willing to rev it past 7,000 rpm. Obviously the rpm drops with bigger motors, and a 572 with B1 heads might peak below 7200? If you go 4.5 bore then consider the B1Mc, but they are not required, just worth more hp.