My car's up to 167k mi., and going strong. Did the head gasket etc. recently, and she's running as-new. I change my load leveling fluid regularly, and have had no problems with that system...I haven't even done the nitrogen cells! Front shocks are fine, too. I have replaced almost every bushing in the front end (as well as the lower ball joints & both tie rods) so she's plenty tight. Gonna keep that car forever!
As to the rear suspension, be advised that teh '86'87 300TD W124 wagon did not have load-leveling, so there's a potential source of parts.
Good luck with your choice!
"If everything seems under control, you're simply not going fast enough" --Mario Andretti
1995 E500 street car
1986 Porsche 944 Turbo S track car