Joel:
I'd suggest keeping the same rear axle length & using a thinner locknut on the left side, and adding spacers on the right side.
If you hunt around you can find a C-Record or Croace d"Aune (spelling?) rear hub locknut. It looks just like a NR locknut, but is 5 mm thick instead of 8 mm. Then add 3mm to the right side and re-dish your rear wheel.
I was able to get a couple of the 5mm locknuts from Bicycle Classics a few years ago (thanks to Michael Kone). Otherwise, you'll have to hunt around. You could try Loose Screws, or your LBS if they have any vintage goodies.
Maybe you know a clever machinist who can grind down a standard locknut & grind new flats for the cone wrench. But that's the hard way.
regards,
Andrew Gillis
overcast in Long Beach, CA