I had urethane bushings made for the 140 chassis as I described but they didn't last over my test period of a year. They still function fine but the centers are loose and we will have to redo them some way. The guy who does this makes and markets bushings for BMW.
The problem with these bushings revolves around the reason one tightens them under real loading. The flex in the front end is dependant on the ability for the inside and outside of the bushing to deflect the amount necessary. This is done in the rubber bushing by flexing. The urethane bushings have no flex so something has to give. Eventually the inner sleeve rotates in the urethane. The bushing guy and a machinist and myself have been pondering the idea of building a joint from two small tapered wheel bearings. Its not a front burner project as I basically see no need for the wheels except cosmetic.
Bosch Master, ASE Master, L1
33 years MB technician