The "Black Widow" uses a four shock setup for the rear end. The half ton truck rear is two inches wider and one and one quarter inches longer than the production unit. This all needs to be mocked up before final installation. The axles, bearings, and flanges seem to be twice the size of the of the standard 1957 Chevy unit. These photos show the special parts you need. They are no longer available, so the "old guy" needed to make them.