We have similar mods, though I have GT-40Y heads and a Steeda #19 cam. Here is what 6lbs of boost/7" crank pulley/power pipe from a Powerdyne did for my car:
http://www.msnusers.com/MustangMembe...hoto&PhotoID=5
My air-fuel maxed around 11:1 on that run.
With only 6lbs of boost, no crank pulley, and no power pipe my car did this on the dyno (the first and lowest run was done prior to any tuning):
http://www.msnusers.com/MustangMembe...hoto&PhotoID=8
Not sure how well your heads flow but with a good supercharger and tune, you shouldn't have a problem putting up good numbers.