451 BB build OPINIONS!!

Not a realistic goal with those heads. If you're not under budget constraints you'll be looking at lots of porting to reach that level, not to mention the cam and valvetrain that's going to require. I would be starting with a set of Indy SREZs with a mild port cleanup, run the Diamond flat top, a port matched M1 with a spacer, and a solid flat tappet with lift around .630 and at least 250°@.050. You're basically building a light .060 over 440 here. So for 600hp it's going to need a good head and the power will be up in the rpms.