I recently gave up on the fuel gauge in my 1980 RC as it was not that accurate.  It was the last factory gauge I still had after replacing the Oil Pressure, Water Temp, and Amp to Voltage with aftermarket gauges.  I am guessing that the 5 volt driver on the back of the factory circuit board was on its way out.

I replaced my fuel gauge with an fairly inexpensive one from Equus (found on Amazon.com) and so far it works great and it was easy to install.
There is a black face and a white face gauge from this company each for $20 or less with the right resistance for Chrysler.

If you are having problems with your factory fuel gauge this might be a cheap alternative.  Try searching for "Equus 8361" or "Equus 7361".