In the 71 Plymouth, Chrysler FSM it is in the Hemi engine wiring diagram page 8-157 Fig 13. where it shows the sending unit, and it is a separate wire that can get lost. Frank is Roger Gibsons partner, and they do some of the most accurate restorations around, and they also sell some of the most accrete repro parts there is. They sell this resistance wire. The gage can fluctuate without it. That's why I asked the OP if it was missing. And everybody knows Donald Duck is a ferry, and that Daffy Duck more of a mans duck.