Rebuilding the rear end. Putting the thrust washers on the right side of the differential. When we put the right housing on, and put in the bolts and tighten them, it spins free with a slight drag, but has a tight spot 1/4 to 1/3 of the way around. It will still turn, but it is more difficult in this spot. Is this a problem? if so how is it remedied?
I put a folded sheet of paper in between the housings to simulate the gasket. Problem solved, no hard spot.
Is the carrier square? Sometimes the side to side measurement varies. Easy enough to true up on a lathe. Check to see the steel thrust plates seat well in the housings, some are warped. The brass thrust washers need to be the same thickness all around as well. If those three items check out OK, do what Doug suggests, there should be no tight spots. A little extra side to side clearance doesn't hurt a thing.
If you're using a gasket already, consider using two. Each one is 5 thou thick if I recall, that should do the trick.