The way mine is routed to the trunk goes like this.
-Remove battery- Battery tray and tie downs.
-Get a ample amount of wire, were talking like AT LEAST 8 feet just for shits and giggles, it can be cut down to the proper size when you figure out where you're putting the battery box.
-Take the power wire from the front battery source, and your new wire will take it's place and run that through the PS fender, there will be spot inside the PS fender/PS door sill that you can then route the wire through. (Mine comes down right next to the ECM on the PS floor)
- Run that all the way to the back, tucking it where ever your heart wants to hide it
- From inside, you will end up in the trunk, mine comes out basically between the cargo hole to the trunk
-Run that under the trunk carpet, or along the body under the carpet
-Put a battery cable end on the end of that Power wire
-Find a suitable place for a ground strap to be bolted in and secured
-Place battery cable end on the Ground wire
-Place battery in box, and connect.
Fin