Finally back to to this project this weekend. Had the alternator tested and it was fine. The ground test seemed to be fine. Put it back together with a new voltage regulator. Took it for a short drive and all was good. Let it idle in the driveway while I watched the ammeter. After about 10 minutes the meter pegged again. I guess the problem is somehow heat or time related and thus didn't show up on the alternator test. When I shut it off the alternator was very hot to the touch, hotter than the valve covers.

I'm ready to just spring for another alternator and voltage regulator to see if that solves the problem. Anything else I could check before that?