Diamond Back tire has some interesting 15" choices, specifically designed to look more or less period correct. They have an interesting process to bond white walls on modern radial tires, if that's of interest. Just watch the load rating, in any case. Diamond Back 15" Tires

1947 2nd-Series GMC FC152 3/4-ton
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1953 Chevy Bel Air Sport Coupe Powerglide