This chart shows recommended wire gauges for run length and amperage:
https://www.bluesea.com/resources/1437
The TL-DR is that if you're okay with a 10% voltage drop, 4 gauge is suitable for runs less than 20 feet and below 100 amps, 2 gauge to 120 amps, 1 gauge to 150 amps, and 2/0 to 200. If you want only 3% drop, those amperages go to 80, 120, 150, and 200 respectively.
I don't know your air bag system, but generally the draw you have to accommodate for the battery lead is the starter, which may draw 150 amps or more at 12 volts -- and even more, of course, if the voltage drops due to a thin wire.
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