I have taken a different approach you may want to consider. I also love the W124 and bought a 1994 E420 that I now call an E420+ because it has 500 suspension with the exception of the hydraulic self-leveling set up in the rear. The E420's in stanard form are way too softly sprung but have a fantastic - and powerful - engine. 275 horses are plenty if you convert, as I did, after much research.
I am delighted with the result which looks and handles great. The relative economics are compelling. The other "responder's" point about parts is true; rear sway bar bushings on the E420 are $4 each and $27 each on the 500's.
I have a 1986 190E 2.3-16 which has the same rear hydraulics as the 500. Boy are they a tedious and expensive pain. I am retrofitting an Eibach rear sway bar and to-be-determined rear shocks to get away from that system.
1986 190E 2.3-16