Need help finding one particular wire...

If I understand what you did?????

You used the "crank" or "start" wire feeding to the start relay to act as an ignition bypass?

You CAN NOT DO THIS unless you put a series diode in the wire leading to the ignition. That's because the ignition -- when running -- will backfeed to the starter relay

It should not be that difficult to trace down the original wire---don't you still have the factory connector coming off the ign switch, in the steering column?

no I did not do this. its factory (stock) on almost all mopar products from early 60's on, there is a seperate terminal on the relay for the brown ignition wire, it DOES NOT hook to the same wire as the starter!

on a fatory mopar ignition its where the power comes from in the start position, I believe points have this wire as well. if you change to another type of ignition system you need this wire! or the car will either crank and start when you let off the key or not start at all