I can't help ya on factory numbers but just for your inforation , the wheels wheren't always centered in the fenders on factory measurements . You may want to mock up the truck with fenders and bed and measure what it will take to get the wheels centered in the openings . I had to add about an inch to the ladder bars on my '38 to get enough adjustment to center the rear axle . It just didn't look right with the wheels in the stock location .