i have a 68 270 column shift auto, might or might not be the same but my reverse light switch was on top of the sterring column right by the firewall, two wires go to it, purple and white, has a plug. try un plugging it (if it is there)
was held on with 3 or 4 nuts. do not know if you can get a replacement. but if it is located there, you should be able to put a modern switch in the tranny and make the lights work off it.