From what I had read in the 1957 Chevy truck info on gm heritage center I was expecting 22.5 wheels but maybe these were an option.
The 22.5" rims were "standard" issue tires...the 20" split rims were optional.
Your truck has the Firestone RH-5 "widow maker" rims...you probably won't find any tire shop willing to work on your rims as they were outlawed decades ago and the liability would be way to high.
Mike B
