We have a '67 326 with original rally gauge cluster. We have been unable to get the temp. gauge to register correctly. We've put maybe 4 different sending units on with no accurate reading. One read consistently 20* low, the others read consistently 20-30* high. I just changed it out (again) with a new Standard sending unit and have a 20-30* high reading. All of the sending units have come from different sources, and all were for gauge clusters.

I am comparing the gauge to an IR thermometer measured on the intake manifold next to the sending unit. The car has never, and does not run hot - although the gauge reads otherwise. It is uncomfortable driving with the temp gauge reading so high. We are trying to stay with a stock appearing interior, or I would simply get an aftermarket gauge.

Anyone have this problem and resolved it? A sending unit for a different application? A resister wired inline?
I also recently added a "ground strap" to the gauge cluster as the wire above the high beam was being problematic.
TIA - Cal