It'd be fun to make a darkroom out of one of these. You could just re-sheet the sides with no windows and then paint it like a Hormel canned ham going down the road.
My dad fixed up one like this in the 60's. I seem to remember bunk beds in the back, a 2 burner stove and an ice box on the driver's side and a little closet on the left as you came in the door. He built a nice dinette in the front with a table that dropped down to make another bed. It had surge brakes, too.