If I were you, and like the car and the way it drives, I'd keep it! I have a 1979 myself, and really like it. I installed the digital servo, and it works great - you may need to replace a few vacuum pods, and I found two defective vacuum check valves under the hood near the driver's side hinge, they were not "checking", probably the rubber check valve inside was hardened. I haven't had mine out since last October, due to the rain around here (I prefer to not drive it in the rain as it's very pristine), but with the hardtop on it is totally rain-tight and has no wind noise. I also have an '82 380SL which I drive everyday, and it also is completely rain tight. My '82 has a 560 engine and tranny installed, and it has great performance, while giving pretty good mileage for such a large engine.

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Richard Wooldridge
'01 ML320
'82 300D 4.3L V6/T700R4 conversion
'82 380SL, '86 560SL engine/trans. installed
'79 450SL, digital servo update
'75 280C