Single tank to Dual tank

[mattshea125]

Hey everyone. I have a 1978 K20 and was looking for some information on adding a fuel tank to a single fuel tank truck. I have a bed from a dual tank truck and would like to add another 20 gallon fuel tank. The truck does not have any of the wiring, switch, or transfer valve. I would like to stick with the factory switch and transfer valve if possible. Any information from someone who has already done this would be much appreciated. Thanks