Couple things here:
First, his car may run like crap, but I'm sure that it is still salvageable. Granted, it does require some work, but on the all, it will still run good. You should try to drain all the oil and put new oil/filter on a couple times. I'm pretty sure by the sound of it that some antifreeze got into the chamber. Basically, you need to get the antifreeze out of the oil. This is similar to blowing a head gasket without actually blowing it.
Second, you won't gain that much from a 94-95 supercharger. I've done it at the same time that I put on 1.73 roller rockers. The two combined, maybe 15-20 hp. The newer style sc's don't have an initial huge impact on hp. They do have more potential than the older style does. Specifically, porting. There is nuch more that you can do in that area. And you don't need everything above the heads. All you need is the sc and the inlet plenum. (The thing that is right behind the throttle body and attaches to the back of the sc). That is it. You need to be careful though, because the vacuum setups are not the same. You'd be short a vacuum tube when you put the early style sc on the newer supercoupe. Specifically, you will be missing the vacuum tube that controls the diaphram on the back of the sc. That's the thing that shuts when you got to WOT. Having that tube miising would not be that good...
...And you won't be able to do the exhaust without getting a newer (92 and up) style gas tank. But that exhaust isn't any better than the early style. Get it done at an exxhaust shop. Cost will be less than the SCP exhaust and will flow just about as good. Search the forums for exhaust and you will find a lot of info.