Polarity is an easy check. You fire the car and check the timing. Swap the connector wires, fire it and check again............Now, if you have an Analog box, the wiring that gives the lowest timing number is correct. A Digital box, will be wired correctly with the highest number. The difference is usually 4-8 degrees. Also, if you have a "locked" dist, or a crank trigger and the timing "backs up" as you raise rpms, the polarity is likely backwards.
