My 451 used the Mopar M1 for the 4150 base carb, and I ran a 1" open spacer on it, topped with a 1,000cfm Holley HP carb. I thought it ran very good, but have no other intakes to compare to on the same engine. It did fit under the power bulge hood if the '71 Charger.

I bought an Indy -? (single plane 4150 carb, "b" block) intake and it looks only slightly taller than the M1 without the spacer, and shorter than the M1 with the 1" spacer, but it is setup for the MW ports. The Indy has the injestion bosses cast in the intake, and I may go fuel injection in the future