The VERY FIRST mod I did with both my Gen 1 and Gen 2 Vipers was to install a convex spot mirror on the driver's side. It's not that necessary for street driving, but once you put a 5-point harness in, you can't lean forward enough to cover all the required field of view. For the '99 model year, they put electric mirrors on the car as standard. In case you missed it - the Gen 1 Vipers didn't even have door handles on the outside of the car, and '92-'93 only had heater/defrosters from the factory. It was all about the most rudimentary, purist driving experience.
96 GTS - some exhaust, brake and handling mods.