RB, your truck originally came with 5.50x17 tires. Your current 5.25/5.50 tires are actually a blend of the 5.25 tire used on the Standard cars and 5.50 tires used on the Master Cars & 1/2 ton trucks in the mid 1930's. Tire manufactures blended those two tire sizes to reduce inventory and let one tire fit both applications (more than likely during WWII rubber shortage).
Mike B
