Anyway, I have connected up the batteries for the time being just to get it going.
Dont mind the messy wiring, this is just a temporary solution until the rest of the parts arrive.
Basically, just connect the batteries in parallel. Positive to positive and the negative to the ground. U can use any part of the chasis as ground, as for me I have choose to use the strut tower as my grounding point.
As what I had in mind, I was able to place back the 'boot box'.
Running the wires to the engine bay take a lot more effort as I had to remove all the seats to run the wires under the carpet.
I had choose to drill a hole at the firewall to run the wire through. I have clear area just next to the air-con exchanger drainage. Remove the glove box first to make your life easier if u want to drill a hole to run your wires.
I used a proper wire grommet to prevent water from entering the cabin and also to prevent rubbing on the wire.