Edelbrock perforner rpm vs air gap

We built a 408 with a gasket matched Air Gap and it made 497/519 and was a fun hot rod engine but I'm sure we left power on the table by using that intake (that's what I had also). We are building a 416 now with ported W2 heads and will be going with a Mopar M1 single plane intake. With a little work to the intake and a solid roller lifter cam, we are hoping to make close to 600hp with this one.

As I understand it, dual plane intakes are designed to boost low RPM torque. The 4" arm provides plenty of that, but needs more air flow at higher RPMs. A ported single plain would be my choice. The two intake choices you posted above would sell quickly here and pay for your new intake.