Well....being the "I know I can fix it" kind of guy I am, I went ahead and looked under the dash on the driver's side. I can't say I wasn't warned.... lol. To my surprise, there hanging down was a ground wire connected to nothing, and 2 wires from a plunger switch by the door. One of those wires was chewed nearly through, but neither of them was connected to anything.
There are 2 plunger switches on my door; one works the interior light, the other which is what those 2 loose wires are connected to... what is that supposed to go to?
Anyways, since I had to pull the speedo because of a flutter in the needle, I went ahead and pulled the tach and speedo. The tach only has one clamp; one is missing. The speedo has both. When I pulled them out and took them apart, there was a fine grey dust of some kind coating the inside of the housing, and a sort of haze on the inside of the glass. I cleaned out the inside of the housings to remove the grey dust from the white paint, cleaned the bulbs and made sure they had good contact. I used Nevr-Dull to clean the chrome and cleaned the glass thoroughly. Now the instruments look like new and the lighting is decent. Definitely an improvement.
I also found what looked like black junk of some kind on parts of the gearing in the speedo mechanism. I cleaned the gears and put a drop of 3-in-One oil on them and everything seemed to move freely. I didn't finish until too late to do a road test but hopefully the needle flutter is now gone.
I cleaned the dash housing that holds the speedo and tach and that whole area with the cleaned instruments looks pretty darned good now. The glass on the instruments is so clean you can't even tell there's glass there unless you shine a light on it. I'll take a picture tomorrow when I have some daylight and can take a pic without flash.