Quick update:

Started it this morning, battery light on. Instead of running to have alternator tested, I took the battery terminals off even though they looked good. Wire brushed the hell out of them and put back on and tightened.

Started truck and no light! Laughed at myself because I thought there was no way it was the terminals. Let it charge (14.1 volts) for about 20 minutes and shut off.

Just went out and started to run some errands. Light is back on! Ugh. Going to let the engine cool down and then pull the ground connection off of the alternator and wire brush it. Going to inspect the 4 wire connector too. Then if that fails, off to Autozone to have the alternator and battery tested.

This thing makes no sense. Driving me nuts. Thanks for the suggestions though.