The dwell meter is simply connected between the CO test point and the battery. The CO test point is the green wire with white tracer adjacent to the red wire with whire tracer which are in a common connector on the right fender well of the 740 series. This two wire connector is usually just in front of the coolant reservoir, and nothing is plugged into it. Adjust the mixture screw in and out until the meter needle makes equal sweeps. Then turn the mixture screw in two to three turns for improved cold running. Instead of the dwell meter you can use Volvo tool number 9995280, which is simply a diode in series with a 750 ohm (or close) resistor. I used a 680 ohm resistor when I made mine, and the led flashes on and off equally when the mixture is properly adjusted.