Reverse Light Help!

[Italia's 67]

Ok so I've searched all over the net and the forum and I can only find partial answer to my problem. Heres the scoop.

67 C20 originally had a 4 spd manual now has a 700r4 from PO. New steering column with NSS w/ hook ups for back up lamps. The problem is there isn't a harness in the cab for the back up lamps and I couldn't find anything near the tranny. It appears that the light and dark green with a couple of other wires just go from the fuse block through the firewall down the frame straight to the tail lights. everything looks factory and unaltered.

I need help in figuring out how to hook the circuit to the switch.