YES, thanks, that's a big help! From what you measured, it looks like the 300mm rotors (500E/500SL/320SL early model R129) will fit any W124, including my diesel. But the 320mm (600SL) front rotors will NOT fit without the late model lower control arm, assuming the 600SL calipers fit the 124 hub/knuckle properly. OR, the 600SL brakes work with the old LCA, and the R129 hub+knuckle (which is exactly what the 500E has). Basically the same deal as the E420 rotors. I need to measure the 124 hub to compare to the 129 numbers below. I'll add the data to my spreadsheet too.
For the record, I measured roughly 44mm from back of flange to the inner braking surface sweep area on the new E420 rotors, and 38mm from back of flange to the inner braking surface sweep area on the stock 284mm rotors. For the stock LCA & hub, the number needs to be about 40mm or less or the rotor won't clear the ball joint.
