Why are you looking for the M1? Hood clearance? There are for sure better manifolds out there, but if hood clearance is what you are after I can see why you are looking for an M1. We gained a considerable amount of power going from a 4150 M1 on a customers car to a victor 383 manifold modified to accept a 1050 dominator at the time. Not all of the gain was from the intake of course, but it was a contributing factor for sure!

-Kenny