fuel gauge wiring

Hello everyone - first apologies if this is in the wrong forum. Trying to button up the instrument panel, and I cannot find the yellow-white wire that oes to the fuel gauge anywhere. I seem the loom coming from the sending unit and up the side of the driver door, but not a singe wire in the loom is exposed that is the prescribed color. It's a 73 Mach one. Any help or ideas on locating it would be greatly helpful.

If I'm no mistaken as well, the negative wire should come off the negative post the oil gauge. That's assuming I'm reading schematics correct.

Thanks again for any and all help!

Sometimes the wire is colored black. Look for a thicker wire than normal near the plugs.