You have to remember though, moving the battery to the trunk and putting it on the passenger side has twice the effect of just taking the battery weight out of the engine bay. Not only are you subtracting the weight from the front and over the driver side front tire but you are adding the weight back on over top of the rear passenger tire. This helps balance the car both longitudinally and laterally.
Plus it gives room in the engine bay for cool things like a turbo or aftercooler water tank
To do it with the shutoff you will need to run two lines back to the trunk, one with 2 gauge, and one with 4-8 gauge.
You disconnect the line from the alternator to the fusebox and run a line from the fusebox to the switch. This is 2 gauge. You need a heavier gauge for this wire cuz it will see the larger current during startup.
The 4-8 gauge cable runs from the alternator to the same post on the shutoff switch.
Then the other post on the shutoff switch goes to the positive lead of the battery. The negative is grounded to the car's frame. I hooked it to the back bumper cuz I could actually get a good hole through there. Make sure to use a grommet.
You will need to seal the box and run a hose through the floor of the trunk for a vent.
I ran the cables through the grommet on the driver side of the firewall where I cut a hole through it. Then run them under the door, just like sub wiring.
Don't use the summitt relocation kit with the plastic battery box. It isn't sealed and it isn't even big enough for our battery's. I'd suggest grabbing one of the sheet metal boxes.