Bought a switch for the extra tank gauge

[Kurt Combs]

Went to Pick-n-Pull today and purchased two gas gauge switches with wiring (one is a spare). Neither donor vehicle had electric tank controls, the switches only controlled the fuel gauge by selecting which tank was being read, not the fuel source. The switches are Ford parts, correct to the vehicles, with the wires for the tank selector valve taped over and not used. They plug into the wire that comes from the cab tank through the A pillar and then into the dash harness. The extra gas tank has an orange wire with a yellow connector that plugs into the switch's wire loom. Does anyone know if the wire to the auxiliary tank is under the dash, unused, even if the truck did not come with the extra tank? That would be so cool.