All 4 speed Saginaws have the 3 shift arm pins coming out of the side cover.
Muncies and BW T10 4 speeds have only the forward gear pins in the side covers. On both makes the reverse gear pin is located in the tailshaft housings.
Saginaws are all cast iron from end to end, Muncies are all aluminum except for the spacer plate between the main case and the tailhousing, and the T10's vary in materials depending on when they were built and by who - original Borg Warner or the currently made Richmond T10.
