Here's what I found for question One;
This has a schematic
http://67-72chevytrucks.com/vboard/s...d.php?t=629061
https://www.67-72chevytrucks.com/vbo....php?p=7414012
The dark green wire is the power feed that runs from the fuse box to the switch. Then the light green wire goes from the switch back to the lights.
With the 4-speed trans, those dark & light green wires both run through the engine harness bulkhead connector on the firewall. That takes them outside the cab and to a 2-terminal plug that connects to the switch on the trans. Inside the cab, the light green wire just runs a short ways from the engine harness bulkhead connector over to the rear light harness connector and from there runs to the back of the truck.