273 that runs great, sometimes

Yeah - very common and shouldn't mandate a "complete rewire" unless you want to. Unwrap and expose/inspect the harness that runs adjacent to those wires for their length. If they are the only ones damaged (and probably are) then get the right color and gage wire, splice in (solder or solder/seal connectors) and then re-tape the areas of the harness. Then do the upgrade, and retape.