[ajcolv]

Thermostat won't add power, just make the car run cooler. You don't want to get pullies, because they can't be used with the supercharger. So far the only aftermarket intake that I'm aware for the 96-98's is the SVO, and that's pretty costly. If you have had the intake replaced under the TSB, then your stock should be okay for a while. Check with others that are S/C'd.

The gears and exhaust would be worthwhile. Since you know you're going S/C stick with the 3.73's. If you want a cheap mod that has good gains get the PI cams. They can be had for about $150-200, and are supposedly netting about 10-15 rwhp.

Other then that look into weight reduction and suspension mods. You don't need HP to go fast. Just ask Mustang92 (Bill).