1968 Dart gauge help

Thanks for all the answers you guys! I did wonder about your about answer#5 67Dart273.
I did try to loosen the 3/8 top nut holding the red wire and it wanted to spin and was somewhat loose/wobbly.I had to use 2 wrenches to back off the top nut. Could that be the issue? A possible broken internal stud! Also, where are the insulating washers supposed to be?