I dont think they is too much of an aftermarket for the series 1 motors (95 and earlier)...
The pulley on the series 1 is already quite a bit smaller than the series 2, I believe the eaton is pushing close to its max RPM stock on the series 1. exuast mods, shift kit, and a trans cooler would be my first mods. after that if availble pulley/intake mods, and so on