Falcon64,
You are absolutely correct about the spark control, and ported vacuun source is plugged on the 68 carbs. They also have a larger venturi as well, so they flow more. As far as the resister wire is concerned, the colors are different for different years. On your Falcon, the wire would be pink, or green with a red stripe. If your Falcon is the same as my Mustang, there will be a bullet conector just priot to the switch. you can pull this connector of, and solder a wire on the male end of the connector. then re-connect the bullet connector. this will give you your 6v source to the coil if you wish, and then run your new wire directly to the pertronix. If you go with a 12v coil, you can run the new wire, and connect it to both the coil, and pertronix, and snip, and tape orig wire. As far as gauge, I ran 18 ga.
Hope this helps.
Bill