I found this for the tank selector.
"The six-port diesel fuel valve is powered by a small electric motor which opens and closes the valve ports. The supply and return ports for either tank open and close simultaneously. The valve is shifted to the front mode (that is, the front supply and return ports open to the engine supply and engine return port respectively) by applying a positive 12 volts to terminal 2 and ground to terminal 1. When the valve reaches the front mode position, an internal switch opens the circuit and stops the motor. Returning the valve to the rear mode is accomplished by reversing the current: positive 12 volts to terminal 1 and ground to terminal 2. Terminals 3 and 5 connect to the front and rear fuel tank senders respectively, and terminal 4 feeds the fuel gauge. In the front tank mode, an internal switch connects terminal 3 to terminal 4, thus supplying the front tank sender signal to the fuel gauge. Terminals 4 and 5 are connected in the rear tank mode. Therefore, a change in the fuel gauge reading (assuming at least 1/4 tank fuel level difference), means that the valve has shifted."
That sould help for wiring the level senders to work. I could probably figure it out, but it's late.