Thanks to the many members of the Classic list who sent me suggestions of how to fix my cross-threaded freewheel and to those who offered me replacement wheels. The hub and freewheel are back together again and spinning properly - tomorrow I take it out for a test ride.
In addition to the offers of replacement parts, I got several promising suggestions on how to repair it. I tried several, but didn't feel confident enough that I wouldn't make it worse using a thread file (suggested by Sid Smith) or patient enough to chase the threads with a small triangular file (Chuck Schmidt's advice).
What did work was Tom Witkop's scheme to take a bottom bracket lockring (same threading) and cutting it and spreading it open so it would fit over the bad threads onto the good inner threads, then tightening it up and backing it out to recut the buggered up aluminum threads with the steel lockring.
I got one free at the bike shop this morning and hacksawed through it tonight, spread it with a screwdriver and slipped it over the hub. I then used big channel lock pliers, gripping at 2 of the lockring slots to pull it back to near original diameter. All this with wheel clamped horizontal in the vise with threads up. First turned the lockring back and forth a bit to make sure it was on the good inside threads, shot a little oil on the threads, then held it tight with channel locks and slowly rotated the wheel. After spinning the lockring off we saw new smooth threads cut where there had only been erratic ridges before the operation.
It still took some care to get the freewheel started back on straight over the lower altitude new threads, but it spun on nice and easy. Tomorrow I'll be riding it to work about 20 miles to give it a little shakedown. I might not use it for a race or long tour, but for daily riding I trust it will be fine.
Again, thank you one and all. This list is a precious resource, especially to home grown untrained bike mechanics like myself.
Bill Mattinson in sunny Sonoma County, CA
ps: I'll be bringing my Masi to the Rendezvous with this wheel on it, but don't ask me to remove the freewheel.