As a guess, the wires probably follow the direction of the key rotation. If so, the first wire should be 12 volts from the battery, the next wire should be the 12 volt feed to the ignition coil, and the third wire should go to the starter solenoid. This assumes you have a gasoline engine, and no starter button, and position 3 of the key is momentary ( spring loaded.) I have a '55 Ferguson, but I've rewired it with aftermarket parts, and I do have a starter button. As such, I only need two positions for my key switch ; off, and on.