Alternator wiring
The more important wire is the lead from the battery terminal to the starter relay. '69 was either 12 or 10 ga, and I would chose 10 if given the option.
Now. How to wire the alternator.
a. I don't know what alternator came on the magnum you have. My guess, and its just a guess, is that its a "revised squareback".
Post a photo or search for revised squareback to see if the alternator looks the same.
For a revised squareback, using the voltage regulator that was originally meant for that alternator would be a good idea. It will be able to handle the higher current that rotor can draw. It uses a ground controlling regulator so it needs two changes from a '69 wiring scheme.
1. The regulator feed must also feed one of the alternator's brush terminals.
2. The second brush terminal on the alternator must connect to the regulator's second terminal.
Your factory 69 V charging circuit looks like this.
A revised squareback will have a regulator that works like this:
3 ga is more than enough for the starter. 6 ga was factory.
The more important wire is the lead from the battery terminal to the starter relay. '69 was either 12 or 10 ga, and I would chose 10 if given the option.
Now. How to wire the alternator.
a. I don't know what alternator came on the magnum you have. My guess, and its just a guess, is that its a "revised squareback".
Post a photo or search for revised squareback to see if the alternator looks the same.
For a revised squareback, using the voltage regulator that was originally meant for that alternator would be a good idea. It will be able to handle the higher current that rotor can draw. It uses a ground controlling regulator so it needs two changes from a '69 wiring scheme.
1. The regulator feed must also feed one of the alternator's brush terminals.
2. The second brush terminal on the alternator must connect to the regulator's second terminal.
Your factory 69 V charging circuit looks like this.
A revised squareback will have a regulator that works like this: