The name change from 500SL to SL500 in 1994 was just that - a name change only. All models of Mercedes went from letter(s) in front to letter(s) in back that year. In the 129 the 119 motor was dropped for the 113 in 1999. The five speed automatic came in 1996. I believe monochromatic paint also came in 1996 - prior to that almost all were a slightly different color in the lower cladding. 1996 also brought a new style interior - with quite a few changes, different gear shift knob, different seats, etc. You mention 92 to 96 - all pretty similar really, with some refinements along the way. If it was me I'd go for a 96 to get the new style interior.