8 3/4 rear end confusion

If you have stock sure grip in a '73, it should be the cone type sure grip. Those don't have a clutch pack to get out of alignment. If you have the clutch type sure grip and the clutch plates turned to where you can't install the axle shaft, the clutches are worn out and need to be replaced. Same goes with the equalizer spacer. The clutch type one comes with two buttons and a roll pin holding them in place. Those pins are commonly broken and the buttons can fall out and jam things, or, fall into the bottom of the housing and the end play can't be adjusted correctly requiring you to pull the third member to retrieve them. The cone type spacer is one piece and can fall out. I suspect you just didn't install the seal correctly and the bearing is hitting it short of where it needs to be when fully seated.