MB has spacers to remedy the problem. They come in 2 or 3 different thicknesses. Fastlane carries them or did.
http://www.allpartsexpress.com/ShopByVehicle.epc?q=1973-MERCEDES--BENZ---0d--/l4_--.--l_diesel-Rear--End--/--Suspension&yearid=1973%40%401973&makeid=MERCEDES+BENZ%40%40MERCEDES+BENZ%40%40X&engineid=1192845%40%40220D+%2FL4_2.2L_DIESEL%40%40220D&catid=Rear+End+%2F+Suspension&subcatid=Rear%20Coil%20Spring%20Shim&mode=PA

The problem with using the spacers you show is they remove two coils from the flex. This can lead to spring failure and a harsher ride.

Worn sub frame mounts or differential mounts can also cause the problem.