A Plastic battery box can be had for $7-$8 bucks at walmart.
You will need some 2 or 4 Gauge Battery Cable. I run 2 Guge in my own car some say you dont need to go that big but i like it.
I would say 12-14 Feet just to be safe i belive i had 12 and it was a little tight, so i actually got a 25 ft. spool to re do it.
And you will need the 2-4 Gauge Lugs to crimp on the end of the cable to hook it up to either the starter and or the Neg cable where you groung it in the trunk.
Normally you should run a decent size through bolt with good size washers on the battery box through the trunk floor but mine is held down with 8 Self tapping Teck screws with washers.
The main Cost involved in doing it is the Cable so if your wanting to do it and save a little cash keep your eyes peeled out ebay for a good deal i just got 25 ft of 2 Gauge for a fraction of the cost.
I ran mine inside the car along the side of the back seat so its hidden and down through the sill plates and into the kick pannel etc keeping it out of view and you dont have the worry of fastening it to the underside of the car.
I want to relocate my battery too but I want to relocate it under the rear passenger side seat. I pulled out the rear seat any ways.
Where do I connect the main power cable coming from the battery? Do I connect it to the fuse box inside the engine bay? If so do I discard the cables coming out of the fuse box that were used to connect to the battery or do I connect the new cable to those cables?