[2FastLX]

You can buy battery boxes with different gauges and grades of cable. I know Taylor has a few options. Go with 2 gauge welding cable. I have mine wired just like Chris stated with the battery grounded right next to the battery box, and a ground cable running from the engine to the frame.

I ran the power wire through the firewall and along the driver's side kick panel to the rocker.
In the rocker panel I routed the cable right along with the rest of the car's wiring by going through the loops inside the rocker.
I then went up under the rear inside quarter and around the back to the shut off switch mounted on the back of my car.
From the switch I went around to the passenger inside quarter to the battery.

I mounted the battery box even with where the back of the seat used to be. The battery sits sideways with the long width of the battery going from side to side. You'll have to check where the mounting holes will be and observe contours in the floor to see where the holes will break through under the car.

Good luck, and don't hit your gas tank