Question about instrument voltage regulator

I suspect I need to replace mine which is the original one in my 67 dart. Today the fuel and temp were working fine. Came home shut off the car and later I started it up to check something. While it was idling I notice the temp gauge was reading high and the fuel gauge was telling me I had more fuel than I had earlier. I have a new fuel sending unit that I installed to get the fuel gauge working again.

So I shut off the car, high temp readings raise a flag. Went and got my infarred gun, started the car and checked the water pump temp on the back side out of the air stream. It was running 180-185. I have a 180 stat in it so I don't think it's overheating. I'm assuming it's the voltage regulater going bad since both the temp and fuel got goofy at the same time. So what do you guys think am I right?

I found a solid state one that plugs in place of the original. I assume I can get to this without removing the instrument cluster.

Edit: Located the regulator on the panel. I was concerned about possibly damaging a gauge, since the temp is deflecting all the way to the right, so I pulled the regulator until I get a replacement.

Edit2: Ok, I had a spare instument cluster with a voltage regulator. I tried that one and I had the same symptoms, gauges deflecting all the way. Is there something else that could cause this other than the regulator?