Yes the cabs are the same between 1/2 ton and 2 ton on the 1955-1959, however one extra does exist on the 1 1/2 and 2 tons. These larger trucks have an additional rocker panel! Their panels are held to and cover the regular rocker under each door with nine sheet metal screws. They even extend from the under door area to along the edge of the cab corner.
Check this page from the 1955-1959 Chevrolet Factory Assembly Manual printed in those years.
Tip submitted by Graeme and Helen Howden of New Zealand.
Their 1956 Chevrolet 2 ton had them missing and the truck was obviously lacking something. They discovered the problem when they found this page during their research.
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