back in the 70s, I knew someone who had an old chevy biscayne that the trunk lid, rear window, and half the roof was removed from, had wooden floors with storage boxes and tie downs in it with a vinyl cover sewn up (including a window) that snapped down on it to close it up. Was the only car I've seen that was a workable pick-up replacement. Hauled tons of stuff in it, but never motorcycles.
Ken.
