I have a 1966 C-10. I will put it like this... With out a wiring diagram, its a lost cause... lol Mine had and still has, Im not done yet, wires connecting to things that dont even run power. On top of that I am having engine troubles, so I am having to hot wire it to work on the engine while I follow the diagram. But, if you get a good diagram, there should be no problems wiring it up. Also, if your truck is like mine, it probily doesnt have too much original wiring. That means that your colors might not be like that on the diagram. As far as connections are concerned, it might be better to use the diagram to see what connects to what, instead of where does this misc. wire go.
Good Luck with you 66'.
