Last year I bought an 86 Euro 500SE at a very reasonable price as it needed work and had been abused by it's second owner. It had originaly been brought into the country by an Air Force General (March Air Force Base sticker still on windshield).The car is diamond Blue (nice Color) and has power everthing and a very good dark blue leather interior I'm not sure if this is common or not in an "86" Euro.
I rebuilt the front end,new belts and hoses, flushed raditor,new rotors,new pads,bebuilt rear caliper, new tires (Yokohames) did some body and paint work.tune up. Then I decided to do a cover off timimg chain. What I found when ordering the chain was instead of a 117 500 Euro engine the car had a 116 Euro 420 engine! I did the cover off.For a long time I felt dissapointment, anger, and felt cheated.
But after driving the car for a year I love it with a capitol L.It gets good milage,has classic style,handles better than any of the 30 odd cars Iv'e owned,It has been very dependable and I plan to keep it till I'm a hundred and twenty.
You said your car had a good body and interior so in my opinion even if you had to put a crate MB 560 engine and tranny in it you would still be on top when you see the gimmick ridden cars being sold at outrageous prices, you have one of the best automoblies ever built bar none.......