I used 12 gauge wire from the dimmer switch to the headlights when I replaced poorly done repairs to the system.
Certainly wouldn't hurt, but to show you how penny pinching GM was ...
The high beam wire from the dimmer switch to the left side terminal board was 12 gauge. It supplied both high beams.
The low beam wire from the dimmer switch to the left side terminal board was 14 gauge. It supplied both low beams which used a little less power.
The high beam wires from the left side terminal board to the individual headlights was 14 gauge.
The low beam wires from the left side terminal board to the individual headlights was 16 gauge. Again, low beams used a little less power.
