I can easily identify mopar u joints, but these gms are little different. For a 1985 c10. I believe they are R3 joints on a one piece 55.5" long shaft from a 1985 C10. Cannot figure it , the out caliper states 1.79" dia cap.
Are R3 joints a 85 c10 replacement?
Can you replace the straps for u bolts at the differential pinion yoke? DR\rill the yoke threads out, if one is stripped. Then use u bolts.