Here is my chance to pitch a R129 , specifically the 97 SL320.

If you can work on a 97 C280, E320 or S320 , you can work on the SL 320 because the inline 6 and transmission are the same between the 4 cars. Last year for the M104 inline 6 ( in the US ), has full electronic throttle not the troublesome half mechanical / half electronic of earlier cars, first year for the 722.6 electronic shift auto trans , last year for a metal key.

Power is adequate though muted below 3,000 RPM due to the cars 4,100 lb heft but it will pull mountain passes at 70+ without running out of breath.

I just happened to luck into my 97 without knowing it was the best / last 320 year. Many _think_ they need a V8 / V12 in these cars so prices are much lower as a result. My 124,000 mile Sport ( AMG trim ) example was $ 6,000 in 2011 and I put another $ 2,500 ish in parts getting it to my standards of reliability. At 135,000 It needs a head gasket due to an external coolant leak and I'm going to rebuild the transmission because it is due.

With any R129, the top hydraulic cylinders are _going_ to need rebuilt due to leaks. I leave the hard top on at all times so that isn't a concern for me. Either top can be manually operated so no loss if you don't change very often.