Headlight harness for 1963 GMC truck

[AZKen]

OK, so you have purchased TWO headlight harnesses. Nothing is labeled "Relay Kit". Which one have you installed? What, if anything, have you "added" to the existing original wiring? Is some of the existing wiring in place or torn out?

I realize you don't have voltage somewhere. We will get to that.

1. You have two firewall connectors. Left side is a 9 pin. This is actually a separate 3 pin and a 6 pin plugged into the bulkhead connector 9 pin. Right?
Right side is a 6 pin. Right?
2. You have one 2 pin headlight feed connector mounted on radiator support, left side. That is the one in your pic that you say no voltage there, right?
3. You should have a 1 pin horn connector, a 2 pin horn relay connector and oil and temp sender 1 pin "connectors". Yes?
4. Have you done any wiring inside cab?
5. Explain exactly how you determined no voltage, and exactly where on truck. With what devise and where probes were touched, etc.
Name the place and the connector as well as a pic, but not just a pic.
6. Have you done anything at the connectors in no.1?

It is VERY hard to diagnose your problems if you have added, altered or removed the original wiring scheme/method per the original wiring diagram. This does not mean a person can not add accessories or an alternator. So try to explain any difference you see from my list and show pics of the differences or anything you see I haven't mentioned. Remember your DETAILED answers and pics are all I have to work with.

Your truck has four headlights as you know. The outside two are Hi/Lo Dual filament. The insides are Single filament Hi. Sealed beam.
You show 90W/100W halogen bulbs. All four would be dual wattage. Depending on how wired, could be 400W! (33A) or 380W (31A) That is unnecessary and overkill to the max. Two issues emerge:
1. Headlight switch is probably rated at 30A and needs to also handle tail lights. Hence the Relay.
2. Amperage generation has to keep up with those high amp draw lights as well as heater, radio, etc. This may require a high output alternator. Relay has no effect on that issue.

A "normal" halogen, LED or sealed beam have about the same amp draw. 4 lights Approx. 20W
All above are at Hi beam. Some LED's are way low in amp draw.

Your Halogen lights will blind on-coming drivers, their passengers and pedestrians.