your timing light might work it's one you'd have to try on the chance that you fry the coil in the mag. If you don't want to take the chance, get a piezo buzzer from Radio Shack part #273-065 or 273-066 ( about $3) and a 9 volt battery same as you use in a smoke detector and wire between the P lead and ground. when the mags points open the tone of the buzzer will change signaling when the points open. That is when you get high voltage to fire the plug on the cylinder that you set your timing to
