fuel sending unit and Selector Valve
 

I have an 86 GMC C15 with dual fuel tanks and im having having a hard time finding a diagram that shows how the fuel sending units and selector valve go together. Searching online i have found wiring diagrams for the selector valve. but none showing how the selector valve and sending units going together. both sending units have three ports. the owner before me bypassed the left tank straight to the motor and completely disconnected the right tank. so im looking for a diagram that will show me how they all connect. or maybe someone can tell me how they go together.