The guy I bought my '48 3800 (with dump box) said his great uncle or whoever bought the PU in Montana and it came to the dealership with NO box and the rear fenders strapped to the frame. The dealership supplied an aftermarket box, dual cylinders, belt driven engine mounted hydraulic pump.
I was told that many companies offered/sold small dump boxes for pickups in that era. My box is shorter than the 9' bed and has a faded, unreadable metal tag riveted to the LF corner of the box.
