Here's the reverse light on my 69 and 68s should be the same. The Reverse light is held into the dash with a big nut on the back of the housing. Much like the side marker lights are installed on a 68. Also notice the ignition light hole. Maybe it's that too if you have the light package?? Disregard the rats nest under the dash, I'm in the middle of diassembling and rewiring the entire dash with new harnesses. Hope that helps!

Cheers