I have been looking at supercharger kits for my '99 Mustang; the engine (4.6 2V) has 20k miles on it and has the following engine-related mods-
Accufab 75mm throttle body and plenum, Underdrive pulleys, K & N CAI
Bassani OR X-pipe, Pypes Racing Mufflers, Steeda Stainless Steel Cat-Back exhaust...