Rewiring the fuel gauge on a single tank conversion

[Neuman]

I have another question on 2 tanks to one. Bought a 83 1500 LB and the previous owner removed the switching valve, now the gage does not work. What wires do I need to splice or jump to make it work.   what wires do I need to

[bd]

If the truck still has both fuel tanks, why not install a new switching valve?

If you're determined to convert to single tank, study the auxiliary fuel tank wiring in the 1983 Wiring Diagram.  Circuit 30 (pink) runs between the instrument cluster fuel gauge and the OEM tank selector valve.  Reroute Ckt 30 directly to the sender in the tank you decide to retain.