67 Barracuda Reverse Lights

when a bulb does not come on, it is one of 4 things:
1. The bulb is bad. Test the bulb and/or replace it with a known good one.
2. The switch is bad. Test to see if there is power going into the switch. If there is, then a good switch will allow power to flow through it when placed into reverse. If there is power going into the switch but nothing coming out the other side when in reverse, then the switch is either bad or it needs some adjusting (if that is possible).
3.If there is power flowing through the switch when in reverse, then there is either a bad wire, a bad socket or a bad ground.
4. If there is no power going to the switch, then I'd look for a bad fuse or a bad wire/connection going to the switch.