John1,
As far as I know, all the Euro 1985 500SEL had the hydroneumatic rear suspension. To find out if yours has it, just pop the hood open and you'll see a yellow reservoir in the front, right hand side, just next to the radiator. If you see this, then you have the aforementioned self-leveling rear suspension, and I believe the entire setup of that suspension is completely different. I don't know any technical details of it, but you'll probably find enough at the link below.
http://www.peachparts.com/shopforum/showthread.php?t=104610
Good luck,
Richard