Mafac Racer's were fine but most went to the Weinmann brakes for some reason. Not sure if it was strictly for weight reasons or because they liked the better fit and finish of the Weinmann brakes.
About 15 years ago I dug through my box of new take offs and sold a ton of them on fleabay. Nearly all of them went to Japan. I kept a few sets for my own use as well as a few other Mafac models from back in the day.
I sold off nearly all the Simplex derailleurs, I may have one or two sets left at best. If I do they're packed away in boxes in the attic.