Will the aux passenger seat fit ,or, will the kit fit any Rev platform or just the GSX?

The 1+1 can fit on any REV. (except the Summit Liquids)

Be sure the sled is 1+1 Capable. Using the 2005 model lineup as a yard stick, the following models are 1+1 capable-

-Mach Z
-MXZ Fan, Trail, Adrenaline, Renegade
-Summit Fan
-GSX Fan, Sport, Limited