1/2" x 20 wheel studs, 5/8" drilled wheels.

WHeels being hubcentric is never a bad thing.
I agree, this is somewhat of a unique scenario though. In my experience with 5/8" studs, the wheels are centered on the stud shoulder, not the hub. I wonder if this is safely replicated by using a shanked lug nut, with an OD that matches the ID of stud hole?