You can download a shop manual and aftermarket wiring diagrams free from MyMopar. I've posted that at least a thousand times
Access the ignition switch connector where it comes out of the column and start from there with a meter/ test lamp
73 shop manual is first year that Ma "reworked" the diagrams for A bodies, for the better or worse, LOL
Start on page 8-153, the index, find "ignition switch" and notice coordinates "B 10" which works like a map on the page edges
Notice the switch has oblong circles "CI-5" This means "connector, instrument panel, no.5" Scroll down to page 8-167 and you'll find a layout of "CI-5" there
NOTICE!!! This is not drawn exactly correct!!! The YELLOW start wire and the BROWN bypass wire DO NOT CONNECT to the same terminal. They actually are TWO SEPARATE SWITCHES in the same housing, IE they are isolated from each other
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This pictures your switch connector as it looks, notice the "pointy end."
The J1-12 RED is power coming in is hot all the time and IS NOT FUSED
Q2 -12 black is switched accessory power feeding FROM the key TO the accessory buss in the fuse panel. Hot in "acc" and "run."
J2-12 Dark BLue is the "ignition run" voltage from the key, through the bulkhead ......to ignition, alternator field, voltage regulator and smog devices under the hood. Hot ONLY IN RUN, and cold in "crank"
J3-12BRown IS THE COIL RESISTOR BYPASS and IS THE ONLY SOURCE OF POWER for the ignition system in "crank." It comes from a SEPARATE switch contact at the key, through the bulkhead and goes to the coil + side of the ballast.
View attachment 1715137933