Welcome!
There should be a rectangular fiber board type insulator installed on the back of the cluster behind the battery gauge that prevents the mounting nuts from making electrical contact with the grounded metal case. And the gauge assembly has plastic grommets surrounding the studs. I believe those grommets protrude slightly from the back of the gauge to help center the studs through (and electrically isolate them from) the cluster case. However, I think it is still possible for the gauge to be installed slightly crooked and allow one or both studs to contact the case, creating a short to ground.
Checking to see if the gauge studs are accidentally shorted to ground can be done with a continuity tester or multimeter (set to the continuity/resistance scale). Simply connect one of the meter's leads to the metal gauge cluster case and then touch the other lead to each of the battery gauge terminals. You should get an open circuit (infinite resistance) reading on both if things are okay. If you get a low resistance reading, that indicates a short to ground.
I would also recommend checking to make sure your truck still has the two little 4 amp inline fuses that protect the battery gauge circuit. If a previous owner has eliminated, bypassed, or replaced them with larger fuses they won't adequately protect the battery gauge and it's wiring (including the printed circuit traces) if there is an overload or short circuit. One of those fuses should be located right near the junction block on the passenger side fender by the battery. And the other should be located at the front driver side of the engine compartment near the voltage regulator. The factory used small SFE-4 glass fuses in black rubber holders (see pic below) but any 4 amp fuse will work.
