Here is GMC Pauls page on the guage wiring for converting to guages from idiot lights. scroll down page. Heres a pic of the wires in the engine compartment for the ammeter. These are the wires with 4 amp fuses inline you will need to add if your truck did not have guages from the factory. The wire from fuel sender plugs into fuse panel, I believe it is marked fuel sender. John
http://www.gmcpauls.com/Tech%20Tips1.htm