4gauge cable mate
you need approx 6m
i intall a 120amp (i think) circuit break next to the battery
just run the +ve cable from the front of the car to the boot, and just earth the battery to the shell at the back
remove the old earth cable in the engine bay
you'll need a distribution block to link all the cables under the bonnet together, DO NOT put a fuse in the starter cable as it'll instantly blow (run it live off the 4gauge cable)
you'll need to extend the starter cable by about 1m