different brake mc use
I recall that early (e12) MC can be used, not certain about later ones.
You'd have to make sure that the actuating rod from the brake pedal projected sufficiently into/out of the MC body.
There would have to be the same number of output ports in the later MC. I'm not sure this is the case... but it may not matter, you could tee off the necessary number. Because the lines are kind of cranky to get on and off, fewer would be nice, but it seems you aren't doing the work yourself.
You'd have to make sure that it would mount correctly, a two-bolt operation and likely to fit.
You'd have to make sure that the volume in the MC was at least as large as the original. Less volume could get you in trouble, more would be nice so as to make less pedal travel, but with the same vacuum booster and pads might need more foot pressure for the same result.
I wonder if the dual booster servo used in some later cars would fit and work on an e9? I once had a 2500 sedan (e3) that had absolutely wondrous light pedal feel and very good, controllable braking, but appeared to have the stock servo. It had been extensively worked on before I bought it, dunno what brake parts combination it had except that it worked great. It also lacked power steering to town driving was good upper body exercise.
