Try taking your truck to a parts store and having them test the alternator. While they are testing it wiggle the connectors on the back of it and the connector at the voltage regulator on the fire wall.
It took some doing on the break to free it up. After a couple days trying here at the house, I took it down to work and put the largest rose bud (heating tip) on it. You would be surprised at what a 2 1/2' flame can accomplish, the whole cast housing was a dull red before it loosened. As it cooled I sprayed the shaft with PB Blaster, it is good to go now. Now to get started on the rebuild of the truck, I need to locate a radiator support for the front and then I put it back together.