Diagram , Photos connecting dashboard

Your dash voltage regulator (Vreg) is inside the fuel level gage. The pin you circled in red is the Vreg output, as I recall. These circuit boards are so simple that anybody can trace the paths to each element. There are no traces on the other side.

I had the cluster in my 65 Dart out a year ago, and currently have my 64 Valiant cluster out, awaiting work. Some maintenance & upgrades you should consider:

1. replace the internal Vreg with a new electronic one. Search "voltage limiter" and "Plymouth" on ebay ($25). There was a post here a week or so ago with links to photos (RT Engineering or such, I recall).

2. Check and resolder the circular connector pins. The solder joints often crack.

3. Sand the ammeter connections and tighten well. Use silicone dielectric grease. These terminals carry up to 40 A, so can overheat and melt if corroded. If you upgrade your alternator, look up my post on adding bypass diodes in the engine bay to protect the ammeter but leave operational, or just bypass it totally in the engine bay.

4. Replace the lamps bulbs with LED type (ebay). Cheap, should last forever, and look nice. Also, sand the copper and grease.

5. Check the speedometer. It should not wobble in the bore, and the needle should move smoothly when you spin it with a drill. If loose, the spinning magnet will eventually grab the aluminum cup and break it (bad) or your cable (better). I had the one in my 65 Newport re-bushed at a speedometer shop long ago.

6. For looks, remove the clear lenses from the chrome plastic and polish. Not easy since you must drill the plastic posts and epoxy back. I also removed the bad chrome paint w/ a soak in Super Clean. I had all dash plastic "rechromed" at Sacramento Chrome for $110.

Good Luck