The Rear Springs on a 123 can be handled with the Strut Type Spring Compressors (I did this but with cheapie Harbor Fraight ones) that you can free rent from AutoZone. So I am guessing it is the same with the 126 ones.
Unlike the Front springs that must be 3-5 times stronger than a Gassers the Rears seem to be of a comparable strangth to any other Car about the same size as a Mercedes.

Later I found out that with a 123 if you let the rear Trailing Arm Drop low enough you can simply pull the spring out. That might also be the same n a 126.

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84 300D, 82 Volvo 244Gl Diesel