No power to coil

The path is ignition switch, through the bulkhead connector, and out into the engine bay to the ballast resistor. Most likely suspects are problems in the bulkhead connector, the switch connector where it is under the steering column, and the switch itself.

Go to MyMopar and download yourself a free service manual

Also while there download one of the aftermarket wiring diagrams, which are not as detailed but sometimes easier to follow.

That 73 manual got there because of the efforts of some of the guys right here