There are several Chevrolet and GMC parts vendors. I purchased a set of hubcaps for my 50 GMC from one for about $110. Brand new repops. Now, I can't believe there is much actual difference between 1937 and 1950, whether in wheels or caps. The GMC script had appeared on GMC trucks from the 30's to the 1954, at least.
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Bryan "Jake" Moran