i d.i.y at a friends acc shop and the cable i ask him to buy. you can go to any accessories shop and ask them for low density cable. there are various range / thickness available and price varies, i think around RM20 - RM35 per foot and for my satria, it requires approx 12 feet. get the one in the mid range, but if u have the budget, go for high range.
connect to +ve at the engine bay. you'll have to drill a hole under the steering in order to re-wire it to the back of the car. insulate the -ve point in the engine bay and tie it appropriately to other existing cable/wire nearby so that it is not hanging loosely.
the hole that u drilled under the dash/steering, close it with whatever suitable, i.e silicon, after u have inserted the cable.
place the cable underneath the carpet along the door all the way to the back and underneath the rear seat into the boot.
after u have installed the battery successfully at the back, pull one short cable from -ve point at battery and solder to car body (metal part). or u can drill a hole and hook the wire and screw it into car body. just make sure its tight.