There were 2 things at play. I think I had set up my test wiring incorrectly and the common denominator was the dash lighting circuit. I'm pretty sure that I touched the multimeter probe to the wrong points. The power surged through the built in lights and then throughout the gauges. At least that's what I'm thinking. I really don't know for sure. What I do know is that after the pop, every time that I turned the truck power (not the engine) on, the gauges all went to their full position. Max oil pressure, max water temp and fuel to completely empty. Also, the dome light, turn signals and running lights wouldn't work. I think I've got the rear end lights and dome light sorted out. I'll try out the gauge lights once I fully sort out the under dash wiring. Still, the only damage that I've found is that one, chafed wire. Very strange.
