If you look high up in the center of the firewall, just a few inches toward the passenger side of the vehicle from the accelerator cable passthrough, you'll notice a rubber plug. From the inside, it looks like a couple of near half moon cutouts in the sound deadening underlay. It is just large enough to pass through a pair of #8s, and if you use Teflon insulated wires, you can get a pair of #6s.
When you wire, go directly to the battery. Don't use the frame or chassis for a ground, or you're liable to create a ground loop.
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