I'd second what Thomas said. However, keep this in mind: If you get it magnaported (which will yield more power than the MPII) you will need to get the MP inlet plenum as well. The stock plenum isn't big enough. That piece will run you $500 with the powdercoated version like the stock piece, more for polished. That has you now at $850, close to the MPII price. And to top it off, you should go ahead a get it rebuilt for longer dependable service. Total price there is $1100 which is pretty close to the MPII price. I"m not sure what it is off the top of my head, but I was thinking it was around the $1200 mark.
I'd HIGHLY recommend the magnaport job. If you don't have the $$ for that right now, turn you attention to other areas that you can mod for less, 75mm TB, 42lb injectors, 76mm MAF, SC top, etc. Even a custom tune on a stock car will give more power. You'll see a gain if you got a stock '89-93 pulley (3% overdrive) for the supercharger. You can 5% (8% on the '95 sc) with opened exhaust. Also a double IC and fan will greatly help reduce the intake temps. There are a lot of things that you can do to get power/reduced times. It's a matter of $$ though. I know this first-hand with 3 young children to take care of. The SC takes a backseat to many things! I'm working on the small stuff now and will one day get the magnaport job on my supercharger. So until then, the little things. They will help in performance and really be there when I go big.