OK it's important we know this, and I didn't realize
Is this here what you have?
If it will start with power jumped as the diagram shows, AKA coil + then this should be simple
All you need to do is start at the key switch, look up the ORIGINAL car wiring diagram and identify the switch connections, then REGARDLESS of whatever color wire is used, trace the IGN1 and IGN2 out through the bulkhead wherever they go. They are also going to have to be connected to whatever is under the hood that needs "run" power, AKA VR power, alternator field, choke if used, and of course ignition system, and that means the coil +
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If you do not have one by now, run over to MyMopar.com and download the two volumes for the 73 service manual. I believe it is Dodge.
This is the switch connector, right out of the 73 manual
S2-12Y is the yellow start wire, goes out through the bulkhead to the start relay one of two "push on" terminals
Q2-12BK is the ACC power is hot in ACC or "run"
J2-12DBL is the Dark BLue "run" wire, hot ONLY in run
J3-12BR is the BRown bypass wire.
(The above two you need to trace out into the engine bay and hook them together, and hook to the coil +. J3 is hot in "start" ONLY)
J1-12R is the Red hot feed providing power TO the switch
E2-18O is Orange dimmer controlled lighting for the shift quadrant
The bottom two, small Black, are for the "key in" buzzer and lighting
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