Robert,
Raise both seats as high as they go. Get a flashlight and look for broken wires in the frame and inspect the condition of the horsehair pads. My pads really did not need changing. My passenger seat had very little wear and no broken springs so I left it alone. The drivers seat had worn out leather and a broken spring frame so I did a total overhaul on it. When you compare the redone driver's seat (with the reinforced frame that I got from Potomac) with the passenger seat it is much firmer and much more comfortable. You spend all of your time in that seat so it is worth the extra money if you can get a stronger frame.
Potomac's numbers are 800-831-7686 for the Maryland location and 800-275-4405 for the Florida location. There are a number of other MB dismantlers listed in Hemmings that you can also call. Performance and Caliber sell new frames for $250 and new horsehair pads for around $110 each. Tex seat covers are around $299 per seat at Performance or ADSIT. If you go to a dismantler get the new style reinforced spring frame from a passenger seat in a later model if you can.

__________________
Tom Hughes
St. Louis
84 300SD
92 300D
86 300SDL