Rear End
If you rotate one axle flange and the opposite side rotates in the same direction, it's a Sure Grip. If it spins opposite direction it's the more common open rear end. Since you have super powers, you should be able to get to the other side before it stops spinning. :lol: Easier with car on stands, tires on, but off the floor.
Check brakes, leakage at pinion and axles ends with drums off, etc. Throw it on the car and drive it. You'll soon know. Good luck!