change in gas and temp gauges

I had a similar problem with a rally gauge cluster in my '67 Barracuda. Installed a new M&H dash harness and did the IVR thing and still had dead or incorrect gauges. Whoever owned this car before me butchered the wiring and troubleshooting is a bear. I finally decided to send the complete dash over to Redline Gauges in Santa Clarita, CA. They will clean, repair, restore everything including a rebuilt speedometer for a very reasonable price. If I still have a problem when I get it back it will have been function tested already so I can start trying to look at the rest of the wiring (again). I have a feeling there is something amiss at the firewall connection. When I got the car somebody had ran a 10 Ga. wire from the battery into the amp meter connection so anything is possible... frustrating. At least I will be able to eliminate the dash gauges, lighting, left turn signal indicator that connects to the 4 way flasher switch, etc. A real head scratcher for sure.