The side panels on the uniline beds didn't change much from 1948 through the end of production in 1985.

Dodge used 3 basic rear fenders. The flat fender military looked like bent flat sheet metal with rounded edges. Those were specific military and were used up to the end of the 68 model year.
The early year beds (48-52) used rounded fenders that looked like over grown trailer fenders.
From 1953 up to the end of production, Dodge used the same fenders used on the Little Red Express trucks. The difference in the wheel base between the truck eras could well be in the front axle location. The 48 trucks were 109" wheel base, but with the 'modern" fenders, the wheel base stretched to 116" wheelbase. Cabs changed in 54, 58, 62, 67, and 72.

The bed sides are a bit more confusing. Up until somewhere between the 1956 and the 1957 model years, the top angle of the bed rails were bent at a 45 degree angle, after that time, and until the end of production, the top of the bed rails were bent at a 90 degree angle.

Early production trucks offered a high side bed side or a low bed side. The low side version went away in 1955. The new 1953 model was a long 116" wheelbase with a 7 1/2' box, as was used on the 3/4 ton pickups. Before 1953 1/2 ton beds were 6 1/2' long. A long bed 1 ton version was available (no length given). There was a note in the 59 model year section that stated that the long bed 1 ton dually used the wider 48-52 rear fenders, one would assume that was how Dodge covered the differences in the wheel base.

In 1959, the standard bed was renamed the Utiline bed because the style side beds were becoming more popular, the name change was to end confusion. Information past 1959 says "the uniline bed remained basically unchanged". This information was from the book Dodge Pickups history and restoration guide 1918-1971. There was a 2 page section that skimmed over the Little Red Express trucks. Gene