1. Hotrod, I did your test, battery voltage to armature post on generator. The generator pulley spun great.
2. After putting the belt back on, I tried your other test, a voltmeter between the armature post on the generator and the block. When I tried this test a couple weeks ago, I got 0.2 volts. You said it should be at least 0.5 volts. Well, I got 14.5 volts today? I double checked everything was hooked up correctly. The only change I can think of is maybe the belt is now tighter since I took it off and put it back on.
3. Your third test, with the field terminal on the generator grounded to the block by a jumper lead, showed voltage climb to about 18.5 volts when I increased rpm before I stopped.
4. 12.5 battery voltage at start of tests, engine off.
13.2 battery voltage at idle.
14.0 battery voltage with increased rpm.
12.4 battery voltage at idle with fan, lights, high beams, and wipers on.
13.2 battery voltage with increased rpm with fan, lights, high beams, and wipers on.

Are those numbers within spec?