First, I suggest to move this one to either E9 Discussion or to E3 Discussion.
They won't. BMW used at least three different angled rear armrests for the E3 back then. And E9 doors are much longer than E3 regular rear doors. To be honest, I never tried or even thought about it. Easiest way to find out: measure the distance between the two mounting screws on your armrests, then do the same with E9 armrests.
Of course you can always drill holes for the plastic nuts into the door skeleton. The correct position is defined by the pull handles. Anyway, make sure before the armrests won't collide with the window crank, the ashtray, the metal trim piece or the backrest of the rear bench. I am not a bit convinced it will work but you may prove me wrong.
The only angled armrests that might fit into your Bavaria are these. They are nylon brown, i.e. beige, but different from beige leather.
51 41 1 823 205 left
51 41 1 823 206 right
They don't mention these parts in gold brown. Maybe there were none.