Chrysler shared many parts across years and models, so a salvage part from a "cousin" or "sibling" might work.
Then again, we are talking about a 37 year old car, so a salvage part might not be much better than what you have. Like the other poster said, you may be able to fabricate one, if you cannot find a reproduction or OEM part.
The fuel gauge problem could be the float, or a sticky rheostat. If you have time to take it apart, that would be the way to know for sure.
If you decide to take it apart, get the car as low on gasoline as possible. The access point is most likely on the front of the fuel tank, if it is anything like the one I did on a 1968 Dodge Dart. Disconnect the fuel lines and wiring from the tank. Undo the lock ring, and the rheostat and float assembly can be removed.
On this Dart, the brass float had developed a leak so it took on fuel and sank to the bottom of the tank, causing an always "empty" reading.
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