S500 used a different rear suspension.

Take a look:
http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1AC0K3S9E1IT1CMTX3&year=1995&make=MB&model=S-350D-001&category=L&part=Shock+Absorber

Do you have ADS?

You just can't swap around shocks you need to find the right one for your car.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200