There is a Wide variety of options, As you already know.
I have done some research in the past on this wiring stuff.
Here are a few places I found and what i decided to use.
Here's a taillight wiring harness.
Link:
https://www.carolinaclassictrucks.com/02br-WH22005.html
There are places that will build them for you.
That's a big leap if you don't know there reputation.
Link:
https://kwikwire.com/pages/ask-an-au...tm_content=60s
Link:
https://streetrodelectrics.com/?mscl...content=pickup
Here's a business that I liked the (History story) Family owned apperance.
Link:
https://oldchevytrucks.com/1967-1972...ess-items.html
There are many place you can get various connectors from.
These are new style connectors, (Probably not what you are looking for).
Link:
https://connectorexperts.com/?matcht...trical%20Plugs
There are places that have the old style connectors.
This particular one is for cars (just an Example) Some of these are the same on trucks.
Link:
https://jcaparts.com/collections/chevrolet-electrical
I decided to go with a Build your own kit.
This is a company close to home.
I really like the visit I had with them.
Probably not most people path for wiring, I'm just showing my research.
Link:
https://coachcontrols.com/index.php?...products_id=85