Thanks again? You make it sound like we're done here. This could run 3 or 4 pages.
So, one car? Not my picture but I saw this at Bonneville salt flats. It's a 50s Spartan with a hatch grafted into the back. It's a car hauler and looks long enough to hold two cars or one streamliner:
http://www.airforums.com/forums/f161/bonneville-salt-flats-59643.html
Radiused edges, aluminum construction—a good start.
Much of the discussion will be matching the drivetrain to the load, search on slowmover and read all his long posts.