I unplugged the tan/brown wire going to the fuse box marked "FUEL GAUGE" and the gauge slowly moved past the FULL mark
Then I plugged the tan/brown wire back in and the gauge reset to the "full" tank spot like it has since I bought the truck.
The tank is full, I filled it up as much as it would take last night. I drove a few miles today and the gauge didn't move much, so I'm not sure if it is working as it used to or if it is now stuck at that new position.