Gauge Cluster Issues/IVR

That started with one person on a Imperial forum web page many years ago. Vendors of solid state regulators simply ran with that info rather than investigate this application/assembly.
Sad and unfortunately all too common situation.

I'm going to leave the IVR and gages alone assuming they pass the remaining tests. Since the fuel gage worked OK, and the oil and temperature senders were getting less than 5 Volts (need to find my notes on exact number) I suspect the problem is in circuit resistance. I need to prove or disprove that.