My car, a 71 road Runner, with a oil pressure gage, has a special , what the service manual calls, resistance wire that is between the sending unit and the harness. It is extra long and taped up into a bundle. It also is shown in the schematic, but only on Hemi cars.My car was a 383 car new. Does anybody know what this wire really does? I'm just curious.

Iirc
It moves the actual needle in the gauge...

EDIT;
It also helps to prevent the needles on the gauges from bouncing around.
A lot of gauges (mechanical OEM) use some type of resistor wire.