Rear control arm bushings are a good bet for what you're sensing. You may not see tire wear as rapidly as the front, due to less force from steering, but eventually it will come. This was my experience on a W126 and the W124 is likely the same in that regard.
It's not too bad of a job with a homemade bushing press using all-thread, washers & large 3/4 dr. sockets.