All of the cars already have aluminum driveshafts in them

How thick of aluminum plate did you use ? Because you used the aluminum plate, I ASSume that you removed the cadmium plated steel backing plate that goes between the engine block and the transmission (You know the one I always forget to install before putting the flywheel and clutch on, hahaha) This way you don't have quite as much thickness as you normally would.. Is that the case?