Using 3 kinds of switches.
The PCM harness needs a push button to activate the starter. You'll put the key to run and then push a start button to crank it over.
The fuel sender in the small Nissan Micra tank can be selected to display on the factory fuel gauge through a splice made on plug G at the back of the instrument panel. The sender is the same ohm rating as the old Dodge sender and gauge.
The 3 extra gauges- temperature, pressure, and vacuum are to help tune the overdrive circuit.
A vacuum switch opens at whatever vacuum level is selected and shuts power off to the OD circuit. As the throttle opens the vacuum drops and the transmission goes back to third gear. The vacuum gauge helps tune that point.
The electrical pressure gauge has a sender on both the engine oil pressure port and the transmission governor port. Both run into a selector switch. The governor port puts out 1 psi per mph so there are 2 adjustable pressure sensors tapped into it along with one of the pressure gauges senders. The idea is to have the transmission shift into overdrive at, say, 42 mph and then the torque converter clutch lock up at 46 mph. With the gauge switched to transmission the shift points can be monitored for possible adjustment. Once that is complete the gauge is switched to engine oil pressure.
The final selector switch is for the temperature gauge. One sensor in the return line for the transmission cooler to see how efficient it is and the other behind the engine coolant thermostat to help set the electric cooling fan switch temperature setting.
The overdrive and torque converter lockup circuit can be switched on with a lighted LED switch. The click clack transfer pump from the 50 gallon tank to the Nissan tank containing the fuel injection pump works on a similar switch with a red LED. That switch can only run until the Nissan tank shows full.
The auxiliary gauges aren't shown. They'll sit on the doghouse until various tuning is complete.