Just remember ,that when you are shimming the diff make sure it is located in the proper spot for consistant ring/pinion mesh and that you can't move the diff side to side at all,but still spin free.
What I do is this:
1. install the pinion gear and bearings first,be sure all is seated completely.
2. install the ring gear/diff and see what you will need for shims (all diffs and cases are different)
3. remove diff and shim ,checking back lash by feel ,you only need a tiny tiny bit ,but you do need it !!
4. after you think it is correct remove the diff and pinion and reinstall diff. can you move it at all as if you are tightening the gear mesh ? If so install more shim to the side it moves towards so it holds the diff snuggly against the gear side.
5. put everything back together and test mesh! If it is good you are done ,grease up your ring gear and install your diff housing to the chassis.
Repeat this for both front and rear and you will never ruin a diff gear again!
You may vaporize the spiders but not the ring and pinion