I don't know about the change over from gen1 to genII starting in 1985. If you are looking for parts for a US car, 84 and 85 500SELs are together and 86 to 91 are together. My 84 was made 11/83. An 85 parts car was made 11/84. They are the same car as far as I can tell. Your discription of the dist in your car is the same as a GenI. GenII cars has a dist without vacuum and mechanical advance. All timing is done in the ign control moduel. The fuel system was different also. 84 and 85 use a warm up regulator and a frequency valve. GenII used a EHA valve on the fuel dist and temp sensors. I don't have an 86 parts car but I do have a 89 and a 90. On the 84 and 85 the rear control arms are cast aluminum and the 89 and 90 have stamped steel control arms. On the 84 and 85 the differential (sp) is bolted solid to the rear subframe. 86 and later the diff is mounted with rubber mounts. 84 and 85 exhaust was a single pipe with 2 cats (one small and 1 large) and 2 mufflers. 86 and later used a larger pipe and converters going into 2 wing mufflers than 2 pipes to a single rear muffler. All mercedes have 2 pipes coming out the rear of the car. Thats about alll I can think of but if you have a question maybe I can help. If your car was made 10/85 it shoud be a 86 genII. Is your car by chance a gray market car or Euro car? All the cars I have been refering to are US cars.

Paul

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84 500 SEL (307,xxx miles)