It's been a few years since we owned a MB wagon, plus my memory not being what it once was, I don't think you can simply put standard shocks on the rear. Estates/wagons weight more in the rear than a sedan (saloon). Though there are springs back there, they are designed to work in conjunction with hydo-pneumatic shocks.

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1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
MBCA member