The first thing that needs to be done is to establish the rear axle centerline. The stock Ford centerline is 36 1/2-inches measured from the rear of the frame rail on 1/2-ton shortbed pickups. In most cases this works fine, but again it depends on tire size and personal taste. It's best to check your wheel and tire combo with the bed installed on the frame to get your own centerline. Whichever centerline you use be sure to locate all of the brackets from the axle centerline to insure they are all located properly.