lol - motor to connect to belts. You are supposed to tap into the negative wire from the ignition coil, its inside the distributor - but would already be a wire from it as the original toyota A/C system works off the tach (rpm signal)
very easy job, - if you want it to look original, find the original rpm signal wire in the engine bay and trace it to your dashboard - besides the A/C amplifier wiring, tap the wire into it and feed it to the gauge signal. You rpm would work.
Or do the classic Pakistani style, buy the cheapest wire from the "parts ki dukaan" splice into the distributor coil negative and fish it through the firewall to the gauge.