[MOTORHEAD]

Well, for one thing, notice the dyno operators 3rd suggestion," take the jets down(smaller) one or two steps" to lean out the mixture.
Ideal air/fuel ratio is somewhere around 13/14 parts air to one part fuel for max power/efficiency. Your carb starts out at 14/15:1 off idle, but goes starts going rich above that. Notice how the mixture leaned out some when the air cleaner was removed. Mixture headed in the right direction (more air without aircleaner restriction) just not enough! The right mixture burns more efficently= higher BMEP (brake mean effective pressure)= more "PUSH" on the piston=more torque and more HP. Mixture is the most important factor in producing max power for any given set of engine parameters.i.e. compression ration, cam specs, etc.
If this doesn't produce enough power, I would "dial-in" the cam (check the cam timing) The lift you have should be sufficient, but the timing could be off. Did you set the valve lash to the proper specs?
On the dyno you could hold a steady RPM, say 4000, and have someone move the distributor and watch for increase/decrease of rpm. Peak out the rpm in this manner and lock down the dist.
Then go back and check your initial timing and max advance. Your timing marks might be erroneous, which is not uncommon.
Good luck, and if your engine blows up, we will dissavow any knowledge of this communication!