Side Plate Troubles

[RoughSilver92]

I'm getting close now with the 5 speed, just a driveshaft and a diff swap away. While taking apart my svx rear end 1 bolt broke off from the rear cover, 1 bolt off one side plate, 2 holes crumbled apart on one side plate, and 1 hole crumbled on the other side plate. The broken bolts, no big deal. The dilapidated side plates, however, mean I will have to use the side plates from my donor diff. This would not bother me much if the shims were the same on both units, but there is one extra shim on one side of the donor. I am thinking I will ditch the extra shim, but how do I check to see if that is correct (other than waiting for it to go BOOM)? I understand how to check the contact pattern, but don't the shims affect preload and backlash also? How do I check those?