Flickering or pulstating Headlights

I have been into the bulkhead plugs a couple of times cleaned them out with hobby files, I got a set of jeweler files which are smaller and try it again this winter. I hope it is something simple and I am just not finding it. Thanks for your response.

Also anyone that has a 66, know of anyway of improving the grounding for the instrument cluster? Especially for the fuel gauge. Thanks