I would check for obvious problems like the wear pattern on the gear, chipped teeth, etc. I’m wondering what the axle originally came out of. No limited slip differential, mini spool locks the rear end by replacing the side gears with a solid steel cylinder with a hole for the cross pin to pass through. If the housing has been properly converted with good welds and true axle ends, and quality welds on the brackets/perches then it’s a screaming good deal even if the only thing you can use is the strange axles and the housing.