I had the good fortune to work on and drive a few of the coupes in the mid 70s. Technical innovation has always been the hallmark of BMW, and one of my favorites was the trunk mounted alternator in the CSL cars entered in the IMSA series. A toothed belt, similar to an OHC timing belt drove the alternator from a sprocket attached to one of the stub axles on the differential. Just one more ingenious way to balance the weight of the vehicle.