There is a difference in adjusting procedures for Timken tapered roller and ball wheel bearings (and barrel shaped bearings?) Pretty sure ball wheel bearings are adjusted a little snugger than tapered roller, which are a little looser than snug.
What kind do you have?
I’d be a little concerned sanding the nut or washer, you should keep washer parallel and face of nut square to centreline of threads. Not saying either is a good solution. If absolutely required I’d trim nut on the lathe a little.
Looking beyond that I’m not so sure this adjustment is an issue, pretty sure it’ll be OK as GM explains how in service manual for that axle. Might be thinking to hard...
