Sorry, I have no idea if my 82 had a 3 or 4 speed auto...it was 20 years ago. A OM617 swap is very popular with the 4x4 guys. There are adapeters to add a Toyota,Chevy, Ford, Jeep, AMC or Chrysler transmission behind them. Adapting a late MB 5 speed to the engine was cost prohibitive (way more than our cars are worth, modified or stock). I have maybe $1000 into the convervsion, including new flywheel, clutch, adapter and transmission. If you care about having an original car, you wouldn't consider it, but if you want performance/milage via an overdrive and a huge choice of gear ratios it's something to consider. I've been told the 700R4 conversions are amazing on the OM617 as far as milage and performance gains, but I'm a manual guy. Anyways back to the question, which should apply to a MB or my kit car (as my wife calls it); what would you suggest for mild modifications to the OM617 to increase milage and possibly performance? I do NOT want something that smokes badly like the 4x4 diesel guys. I went that route on one of my Jettas with larger injectors and pump and hated it, but it performed amazing and averaged about 47mpg. My record was 56mpg...takes out a Prius! I'll be interested in what you think.