I’ve seen guys claim 530-560 hp from trick flow heads on 408 cubes, either out of the box or ported. If you factor 20% drivetrain loss this package is right about where it should be imo, right about 535hp. I don’t think the camshaft is the limiting factor here. I think you’re running out of cylinder head. And it shouldn’t be shocking at all that a nice radius entry at the top of the carb is better than a sharp shear edge. The filter just ends up not being that much restriction.