68 a-body left indicator pulses

The solid burn before pulsing is another charactoristic of the voltage limiter. Now I dont know how gauge voltage can get to a signal lamp but thats where its coming from. There are places where the circuits get close to one another. Copper trace on printed circuit boards is one of them.
I've been wrong before. My quarter bet is placed :)
If you have a standard panel you can pull the limiter can off the board and see if the condition still exists. A rallye panel will be a booger to test.