I still have yet to figure out exactly what you are interested in by what you asked.
Your GM corporate 12 bolt has a ring gear measuring 8.875 (8-7/8) inches, axleshafts measuring 31-5/16 and 31-11/16 inches and having a spline count of 30. I'm not sure I remember right but I "think" the longer shaft goes in the drivers side.
The ring gear is held to the carrier by 12 bolts, same as the cover on the rear of the housing. The pinion shaft diameter measures 1.438 inches, the pinion shaft spline count is also 30, and 12 bolt 8.875 (8-7/8) axle ring and pinion gears will not owrk in the truck axle the car 12-bolt has a pinion shaft diameter measuring 1.625 inches.
Without checking into it further I don't think the car and truck pinion shaft bearings are the same outer diameter so I am not sure if they will be able to swap from housing to housing. You would also have to check the carrier bearing measurements to see if those would be able to swap also.