Well, did some work on the Trooper today. Went in from the underside. Took off the skid plate and went into the loosening procedure for the alternator. Turns out the last person who last put the belts on (they are relatively new) didn't tension them correctly, or didn't tighten the tension bolts properly. They were already loose. So I tightened everything up and began the tightening steps from the beginning. Got the belt tight and re-tightened the bolts. Fired it up and no problem. Let it idle for a bit, cycled electrical devices on and off, no load, heavy load, everything was fine. Shut it down, let it cool off, turned on the headlights and fired it up. No problem (little slower to turn over with the lights on though). In dash volt gauge shows 12+ volts and only a slight drop when putting a load on, but quickly goes back to "normal". Still going to get the batt and alt checked again by a different shop.