Update!

I cut off the perches and made a jig off my old diff to reweld them on the fresh junkyard rear end.

Got it installed yesterday and truck drives great now, no more terrible whining!

Elated to finally be able to drive this truck after weeks of working on it, I picked up some diff fluid today to change it in the jy axle.

Found the attached on the magnet. Not sure where it's from but thought i'd see if one of the experts can chime in.

Rear end works great, LSD works correctly and no noise so mostly curious as whatever it is does not seem to be negatively affecting anything!

 

It's a retaining clip for the LSD clutches. Common for the to pop out when worn.

 

Thank you magnethead!