I believe some SL500 models were equipped with the same brake combos as SL600s, though I couldn't tell you what years apply. I think it's already been mentioned, but you can't easily swap those brakes onto most 4/5/6cyl 124s. Most cars will need the welded balljoint LCAs, 129 or V8 knuckles, and modified or new 129 backing plates. I also swapped in a 500E master cylinder. All told, in order to do that swap correctly, you might need to budget between $1k and $1.5k depending on the used parts prices. That money is probably better spent on other more vital projects.