Actually when new they always had larger size tires on the rear. I know this is true for the 47-54 models. Example, if it had 7.50/20, on the front, it would have 8.25/20, on the rear. If i were you, I'd run 7.50 front, and 8.25, on the rear, if you have the clearance. The larger tire size will help your rpms.
