Maybe the guy who installed and setup the new bearings has put too much preload on the bearings?
I just installed a pair of DrDiff-axles in my self-narrowed 8-3/4" A-body housing and yes, everything feels 'tight', but not hard to turn or feel like binding.

Have your drums, brakes and rear axle checked over by someone experienced. Spacing out a drum for it to clear the backingplate sounds flakey in more ways then one. Something's not right.