Are these special bolts splined to grab the shock mount? I had one spin on the 280, I used a brake adjustment lever (looks like a mini pry bar) and jammed one end under the flat head of the bolt. Then I used the bar to put opposing pressure while turning the wrench. These were the short bolts that are pressed into the shock at the factory, not sure if yours are similar.
It was a PITA, but did the trick.
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72
'02 CLK320 Cabriolet - wifey's mid-life crisis
2012 VW Jetta Sportwagon TDI...at least its a diesel
Non illegitemae carborundum.