They are different, the A833 was offered beginning in 1964 and came with its own cast iron bell housing which can sometimes be found. Later model cars, I don't know exactly when but certainly by 1976 when they started producing F bodies had an aluminum bell housing that includes the A833 bolt pattern but they also went to a larger bearing retainer hole at the same time so if you have an earlier transmission with the 4.3 or 4.8" bearing retainer you need some kind of an adapter which you can find.