Your factory 2-speed rear is more than likely the 6.40/8.72 to 1 ratio. They did offer a 5.83/7.95 to 1 ratio, but that's pretty rare.
9.00x22.5 on the front and 10.00x22.5 on the rear bias tires should be fine on your truck. Radials in 9R22.5 front and 10R22.5 rear are good also!
Mike B
