There are a few mentions of big wire upgrades in these forums in the Audio & Video section. An audio forum would be more friendly for info on the build, but OP was just asking for model-specific help.

We know GM well enough to expect no more copper in the car than they think absolutely necessary. For bigger alternators and multiple batteries commonly backing up high-powered audio builds, bigger wires are defensible if not imperative. There are kits for replacing the three big wires.

My advice to OP would be to just follow the wires and expect some hard work. My perception is that people don’t appreciate the work and skill needed for solid customization until they actually create it.