Wire routing for backup light switch on T-19.

[6t6merc]

I've got a T-19 in my '66. The switch on the tranny has two wires; I presume one is from a 12v source and the other goes to the lights. Can someone tell me how to route these wires? I'm thinking about feeding them through the shifter opening, under the floor mat, and into the wiring at the firewall, but I'm thinking Ford had a better idea. Anyone know?
Thanks, Eric.