You going to drive it or look at it?
Got scracth?
Fuel Economy of the 1988 Mercedes-Benz 560SEC

Just my $.02, but the only way I would consider it is if it was a 1 owner car, I could talk to the owner and he had the entire service history of the car.
Even then, I hope common sense and my experiences with my 88 300CE last year would make me look at the odo and take a pass.
Just a point of clarification. Is that 320,000 miles or 320,000 km?

Jim B. is the one to ask. He knows them better than anyone.