I think what '90 SC is looking for is
1) ease of installation and
2) least amount of out of pocket expenses.
Sure, injectors, MAF would be good...so would a jackshaft pulley, but I think people are getting off the point here. The question is, can you run a '94-'95 supercharger on an earlier model SC without upgrading anything else.
The short answer is "yes," but with limitations. You can't effectively run anything more than an early style pulley as you will encounter higher ACT temps which in turn requires more fuel to counteract detonation. More fuel means larger injectors. No porting on the supercharger...that will allow more airflow...more air needs more fuel...pretty simple there. Same goes for MAF and TB as well.
'90 SC,
My SC is pretty much a street only car. We lost our only 1/4 mile track a couple years ago, and nothing has been done since. Up until a year and a half ago (Got sick) it was driven daily. It would be still except I had another car given to me. I don't race my SC other than at most 1x per year, on average (that's going to the track). Now, just because I don't race it doesn't mean I don't enjoy it. Believe it or not, daily driving is tougher on it than racing it occassionally. So just because it's not a "race" car, it can still be abused like one.
You will be able to bolt on the supercharger and pulley without needing a tune. It's not like you'll be bolting on an MPX with a MP inlet plenum. The '94-'95 supercharger is just more efficient than the earlier style (coated rotors and gearing are why). The main reason for increase hp is for slightly more airflow and slightly less parasitic drag. Those two things combine for maybe 20 hp if you're lucky. My '89 ran a best of 15.2 with the '95 supercharger on it with virtually no other mods. It's not going to turn you SC into a race car by any means.