I have a low side box. attached is the info I found on the internet.
1953-1955 SHORT BEDS Series: 1953 - B-4, 1954 - C-1, 1955 - C-1 & C-3.
New fender introduced. This fender would be used until the stepside beds were dropped from production in 1985. Boxes are now 2" shorter than previous years at 76-1/8" inside length starting in 1953. This affects the bed wood, bed strips, and angle strips and bedsides. New wood floor layout with seven bed strips and eight wood boards. Pine wood was now used instead of oak. Bed strip and angle strip hole patterns changed slightly between 1954 and 1955. Bedsides are still angled outward at the top. "Low side" and "high side" boxes are both available with the "low side" box standard equipment. Tailgates and front panels for both boxes remain unchanged from 1950-1952.