I recently purchased a 40 Buick Super that needs a rear end from lack of fluid. I hear that 40-54 ring and pinion are the same but I don't know how to set up the gears properly. I would like to find a complete rear end but if I cant I was wondering about just changing the center chuck and I don't know if the inner driveshaft is part of the pinion gear or does it separate? Would I have to include the driveshaft with it? Also what year and series would interchange?