What's very telling is the ~20CFM OOTB difference from .400 through .600 is going to be worth roughly 40HP more to a combination with enough cam and compression to take advantage of it, that's a VERY SUBSTANTIAL difference.
That's what I liked too. I'm thinking that with very little work these heads would go 280 plus and I mean very little. Bell shape the exhaust port to get some speed and let her breath.
