67 Dart 270 reverse lights always on...help please

The "bar" and the contacts of the one i took apart had a lot of wear in the places where it contacts. also the grease in the switch was as stiff as toothpaste left on the counter for a week. If you can get some contact cleaner that would be the first safest thing to try but I would bet that wd40 would liquefy the grease and release any gunk in there. Are the contact wobbly from the under side, the contact rivets might be loose and catching?

The only thing I would watch for is that whatever cleaner you use is safe in the plastics.

is the large return spring on the shaft intact?

push comes to shove drill out the rivets ( watch the springs don't fly away there are 2 small and the one large) clean everything, smooth any edges you think might be catching and get some switch lube ( light bulb grease might work) and reassemble using small screws and nylock lock nuts to reassemble.

I have seen a NOS for ~$35.00 on ebay recently but most are in the 65 to 100 range.

good luck