[AZKen]

Hello Tom, I recommend starting new on this wiring thing. OK? Here we go.

Stop testing. Stop looking at fuse panel. For now.
Look at the wiring diagram for 1965 GMC. You will see the turn signal switch. The diagram shows Violet. N(white), Black, Dark Blue, Light Blue, Dark Green, Yellow and Gray wires. 8 wires coming out of the switch. (One extra gray wire probably not there).
Find the connector from thr swich wher Lizzy describes..... and tell us if there are those wires and those colors coming out of the turn signal switch and going to one half of the connector. Do not proceed until you post this information. Make sure you check this website forum often so the time zone difference does not slow us down too much.

We should now go one step at a time at first.
As you know:
The "Turn Signal Switch" is a switch inside the steering wheel/column. Operated by a lever.
This switch has wires running down the column to one half of a connector.
The other half of the connector is wired to the truck/harness.
These connectors are "plugged" into each other (mated).

If any test are given, we will only be interested in finding 12V, not ohms. Unless we want a continuity test, which just confirms if a wire is connected from one point to another. We won't need an ohms value. You will find the Continuity setting on your multimeter. Sometimes it's a buzzer sound.

You need to have a front dual filament parking brake socket/bulb each side. In the rear you need the rear light to have a dual filament socket/bulb each side. Please advise. Also Please explain fully and completely so we can understand this statement "Parking light (separate harness because of law here)"

I see you are doing a wonderful restoration. Good job. I believe your lighting problem is just a slight miswire which we will find as we proceed slowly.

1. Did you buy a complete harness or building your own? If you bought one please give vendor and part number of the harness.
2. If you are making your own, what fuse panel, what sockets, what connectors are you using? Vendor and part number. Explain carefully.
3. Are you using original headlight switch, park and tail sockets, ignition switch, turn signal switch????
4. What is your experience level with automotive wiring?

It's always a bit more difficult for both of us due to slight language and time zones. We try not to wait days for each response if we can. We will lose progress. I will do my best.