I agree with Va.FireTruck. 8.25 X 20, is a good size for your truck. It would have came standard from the factory 7.50 X 20 front, & 8.25 X 20 rear. I've got 8.25's, all the way around, on my '46 Chevy 2 ton, & '53 Chevy COE 2ton.
Spanky Hardy Collector Of Fine Old G.M. COE Trucks & Antique Holmes Wreckers