If you have the old typ charging system then I would change over to the newer chaging system. I used 75 Duster to get the parts I needed to change over to the later model chaging system on my 67 cuda. All you need is between 65 -100 amps I would say.
On the headlight wiring and relays the Painless wires was already made up just like the above picture. All you have to do is hook a wire to the starter relay, one to ground, and the wires come with a connector that you plug into your headlight connector on the back of your exiting headlights.