Instead of firing blindly in the dark, let's actually find out what the problem is so you can fix it
You need to understand how Mopar ignition switches operate. They are actually SEVERAL switches inside the housing we call the "switch."
ACCESSORY Not our concern for this problem is live in "run" or "acc" feeds power to the acc buss in the fuse panel
IGNITION RUN, also known as IGN1, dark blue, unfused, comes out of the switch, feeds power to the cluster and warning lamps, goes through the bulkhead, and feeds the ignition system, the regulator "I" terminal, and on 70/ later cars, feeds the blue field wire at the alternator, as well as electric choke, if used, and some smog doo dads on some models.
THIS IS HOT ONLY in "run" It is COLD in start. The coil gets voltage from this wire THROUGH the ballast resistor
START YELLOW, hot ONLY in start, feeds power to the start relay to crank the engine
BYPASS, also known as IGN2, brown, THIS IS THE CULPRIT we are worried about in this trouble. This is a separate contact in the switch, feeds power only ONE place -- from the switch, through the bulkhead, to the coil + side of the ballast resistor.
During "crank" the RUN wire is cold, the brown bypass wire should be hot, so if the brown wire has a problem, the car will not fire.
EIther it broke and became unhooked, or the bulkhead connector is corroded, or the IGN switch connector or the switch is bad.
Get access to the IGN switch connector. You may need to remove the small trim under the column
Probe the connector for the brown wire, twist the key to "start" and see if you have power
If you do, the problem is likely a bad connection in the bulkhead connector
If you do not, the switch is bad.