Okay, here's the latest. Just dropped off the factory original sending unit at APT Instruments of Bloomington MN. Very nice guy named Chuck owns the place and has previously rebuilt the gauge cluster in my 74 Duster. We checked the factory sender on an Ohms meter, and the resistance readings were all over the place. He's going to completely refurbish it with new points across the rheostat, and new windings inside as well. I'll report back in a few weeks on how it went. He says that the Chinese and Argentinian ones that are repopped are crap, and he has a whole bunch of experience rebuilding MOPAR instruments, so I tend to believe him. More to follow.