Thinking of changing direction with my engine. Opinions needed

The first question should be what do you see yourself doing with the car when it's finished?

IMHO, aluminum heads will tolerate .75-1.0 additional compression before detonation (knocking) will occur. The reason is largely due to the superior heat dissipation of aluminum.

As far as problems with the air gap, they pale in comparison to what I've seen of the Chinese knock-offs.

FWIW, I saw a comparison of the air gap to the M1. Engine was a 300/360 crate motor with Eddy heads. Both manifolds were gasket matched, the M1 had some work done to clean up the plenum as well. Final Results: The M1 didn't beat the air gap until about 5200 rpm.