I'd run a 10 gauge, which should prevent a wiring harness fire in case of an accident or a dead short of a major component like a fuse block feed wire, headlight feed, etc. and still carry the full output of the alternator. They're usually available in the electrical "help" section of most well-equipped parts stores like NAPA, quite often with a round lug terminal made onto one end, and a splice connector to complete the circuit to the ignition switch, ammeter, alternator output, etc. Just be sure to get a VERY good electrical connection where you make the splice to prevent overheating of the connection from resistance.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
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