Kevin,
The voltage regulator might be bum, but I don't see it as a suspect in this problem. Get the truck starting properly again, then address the charging system. It might not be the regulator..it could be the generator, or merely a broken or corroded wire.
What you don't want to do is start replacing things without troubleshooting and determining what's wrong first..unless your brother-in-law is Bill Gates.
The gauges and most other items on your rig feed from the BATT lug on the solenoid. This would normally be a straight shot into the system, but in your case it looks like they have used firewall connectors as a pass-through.
Dink around with your new toy and get to know it. Maybe it just needs some TLC to wake it from its long sleep.
Stuart
