A very nice arrangement that a friend had in similar restricted-width garage circumstances was to install an electric winch on the floor at the back end of the garage. A couple of trial-and-error sessions yielded a nice "bridle" that was attached to the bumper mounts of his car (not a GT40) that was then connected to the winch cable. Trading off the potential of a strained back for rather slow movement into the garage from the winch seemed to be a fair deal. I think at one point my friend was considering installing a removable pulley in the drive that the winch cable could be looped around and used to tug the car out of the garage, but as getting out of the garage seemed easier than going in (perhaps due to a bit of a slope out from the garage), the driveway pulley notion was not implemented.