rpm airgap vs the m1 single plane

It's plenum design is for use of the TQ in class racing.. With the TQ on top, the entrance is OK. Some work can be done to improve the flow with the TQ, but over all, it's OK.
Not to bad for the Holley either, though after plenum work is done for the Holley, it's really nice.

I'm with cracked! You'll improve a little on the 60' times and lose nothing up top. The cam is still a bit mild for a single plane unless you have a dedicated race car ignoring everything below 3500 rpm. At this point I believe the M1 is a little better in HP.