Mike,
Below is an extract from the
1953 Chevrolet Truck vehicle information kit that provides the original specs on what would/could have been on your truck.
16" diameter x 4-1/2" rim width (measured inside edge of rim to inside edge where the tire beads rest) with a 9/16" offset was the standard wheel for 3100's.
There was an optional wheel that was 15" diameter x 5-1/2" rim width with a "0" (or possibly a 1/8") offset. Hard to understand as the document seems to show both measurements???
Anyhow, the 5-1/8 to 5-1/4 outer edge to outer edge measurements seem a little on the narrow side for a rim that should have an inner of 4-1/2".
It's possible you have some earlier wheels as 1941-47 standard wheels were 16" x 4" and optional wheels for those years where 16" x 4-1/2".
Maybe you can remeasure the wheels inside edge to inside edge and report back on what you find? Wouldn't hurt to add some pics if you can of the different wheels to help better answer more questions.
Dan