Not sure about the '55 3800s, but my '59 model came with 18 inch wheels. 16" wheels wouldn't fit over the rear drums. In my case, I upgraded to 19.5" one piece wheels so I could run modern radial tires. It turned out to be the best improvement I've made to my truck.
Oldbolter
1959 Apache 3800 dually flat bed/dump with 261
1956 3800 dually flat bed/dump with 235
1957 3600 flat bed, 350 engine, 700R4, PS, disc brakes, 14 bolt rear with 4.11 gears
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