For the later W124s, MB went to a different LCA design to clear the larger brakes that they installed on the cars. On those later design LCAs, the ball joints are not replaceable -- you have to buy the entire LCA. Unfortunately, there is no good aftermarket brand of late LCA either -- you pretty much have to go with OE to get an LCA that lasts. The aftermarket stuff (febi) is crap.

The early 124 LCAs are available quality aftermarket, Lemforder brand. They also have replaceable ball joints.