You could also try loading the alternator. With the truck running, turn on your high beams, blower on high with the defrosters on and let it run for a good 10-15mins. Sometimes it takes some load and time for the alternator to start dropping the voltage down. You could always take it to a shop and get an AVR test done and make sure they check for a draw. Shouldn't cost too much and it might be worth it, just because of the headaches you've been going through.
LTF