I believe Dieselwrencher is correct on the frame widths. That said there are 2 different rear spring width dimentions on the 67-72 trucks. I know my K20 rear is wider than a 2wd rear with springs. My frame widens behind the cab. If i recall corectly mine is 42.5, the other is 40 i think. So obviously different spring pirch widths on the axles too. If that helps ya any...
