There's several different 12 bolts, more info is needed to tell if what you have can be swapped around. 12 bolt Passenger and truck do not interchange, and there are at least 2 different carriers within each version for the different gear ratios. It will depend on what gear the LSD is set up for as the what can be run on it. The Truck 12 bolt ran from '63 to about '76 (I have seen them in later trucks, up to '80) and came in 5 lug ('71 and later 2wd) and 6 lug ('63-'70 2wd and all 4x4), as well as 2 different axle spline configurations ('63-mid '65 are 17 spline, later are 30 spline).
