Slightly strange head flow question.

one point i want to make. ported 589 heads cant get to big to cause a velocity issue on 392 inch motors. rhs heads cant get to big to cause velocity problems on 392 inches. even if the cam timing is set up for only 5000 rpms if you increase the flow in the lift that you are using you will gain some power. 300cfm will make a increase in your engine.