Intermittent Ignition Issue [66 Valiant /6]

If you suspect the ignition switch is the problem with a no-crank situation, I pull the plug off the back of the switch and use a jumper wire between the BAT and IGN2 to see if it will now crank. If it will now, it's the ignition switch, if it still won't crank (or even click the starter relay) you have a problem further downstream....probably the relay or wiring connection between the ignition switch and the relay. The neutral safety switch or it's wiring is also a possibility.