12 bolt rear axle questions

[1971 cheburban]

I've got a 12 bolt in my 71 c10. My truck was cut in half and a suburban frame welded to it. So the 12 bolt is from a suburban, not sure what year, with a stack of leafs. I've seen the 12 bolts that are originally in these trucks that have the trailing arms and coils that have the tracking arm mount cast into the housing. but mine doesn't because it has leaf springs. Is that the difference between what they call the "CAR" and "TRUCK" 12 bolts, also is there any way to check for posi without pulling the cover, like jacking it off the ground and spinning one tire and the other will spin with it or what?