Henry, I noticed in your post 13/7/15 you have the dash out of your car and a picture posted of the backside. You can see the ground strap from the gauge to the high beam socket then to the center mounting hole. That ground must be good for the gauge to work correctly. Seems to me there have been other posts concerning the gauge ground in the same area. You may be able to search the archives for an explanation from someone who knows more about this than I. I'm not an expert.
On the side, I notice you are in Katy, I have a friend in Sugar Land that I visit every year or so, perhaps you can show me your car next time I'm there. I've been promising myself I will make the 2500 miles trip in the non a/c Firebird but as of yet haven't found the time. It's a bit faster by air.
