Hi, my BMW diff prop mounting is slightly offset, I'm going to have to alter driveshafts anyway, any reason I shouldn't offset the diff mounting position to make the prop run parrallel to the prop tunnel?

BMW may offset the prop for packaging reasons in tin tops, but I can't see why you shouldn't mount the diff in your own chassis to centre the prop shaft in the tunnel. My Sierra based MK Indy worked fine that way. It maybe worth joining a BMW forum to ask about the driveshafts (or find a friendly BMW dealer).