The battery box also houses the main contactor and a cut-off switch. Essentially all electric power can be contained within the box simply by turning the switch off. I also got some gland nuts for the cables to exit the box in a clean and secure way. Cables within the box are just 35mm2 for now, but the longer cables are 50mm2. I'll need to get some more though. The 6m roll of cable I got earlier doesn't reach to the front of the car and back.
Taking the tank out took some doing. First few bolts came off nicely, but just as I though I had them all out I found the last one. For some reason the last one always turns out to be the one rusted out and nigh impossible to remove. Eventually it did give up and I was able to wiggle the tank out from between the handbrake cables. Spilling of some gasoline left in the tank could not be completely avoided.
I also used a 5 V 2.5 A D-Link power brick to top up the the cells which we're a little lower than the rest. Now they seem to be quite happily resting at about 2.95 to 3.02 volts like the rest.