as for rear brake drums the ones on the car way back then were fried and badly scored,they,ll be in one off the sheds under years of parts,found the front ones they look to be stock,back to how can you tell if the locker was in car from new,as was an option i thought heaps of people would have ordered it,i hate the slip in limited slip diffs,direct drive is much better.
I think the only Diff on Option was the Limited Slip type of Banjo,Not a Detroit Locker Banjo Diff,but the Detroit Locker should of been in the 200-1972 LJ XU-1 that had the Sprintmasters wheels,as the Sprintmaster Fitted LJ XU-1 were to use up the V8 XU-1 Wheels,but who knows.
Well the Diff in your car should have alot of grime on it etc,thats if not cleaned up,all depending if housing been cleaned up i Guess,I say best bet is to pull the Banjo Centre Out and see if its just a Banjo L.S.D type or a Detroit Locker type Banjo,The Factory XU-1 had a Red Metal Tag on the back of the Banjo where the Nut is to put Oil in it,has it got a Red Tag.
I have no pics of a Banjo Detroit Locker Center to show u,so u can compare,as they are rare to see,maybe someone on the site might have.