fuel tank did come from australia, it was 1600 bucks I think, but will have to look back.

I chose a relatively small in size second battery, basically, did not relocate much of anything, tipped it on its side (AGM type) and mounted it. the smaller battery is used for starting the truck only, the big battery in the factory tray is used for accessories, and I can kill it overnight. I just use the smaller 2nd battery to start the truck in the morning.

I am using a computer controlled isolator, there are much more simpler systems out there. like I said, my setup isolates the battery from the charging system when winching, this protects alternator.