Harvey, a tow package was available as a dealer installed/over the counter option. JohnPuma, I went back through the pictures I took as I was stripping the car. You can't see the hole when the bumper is on and from the inside the tail light protectors hide but when the bumper was removed the hole was there? Was there a tow package on any of these cars? Maybe this was routing for that wiring?
I respectfully disagree. The license plate bracket mounts above the rear bumper. It fits between the tail lights and covers the gas cap on a 67-68. JohnIt is for the license plate light wire and gromet. The bumper covers it cuz the license plate is on the bumper and so is the light.