Attached are some screen shots of the fuel system in the Boston IV manual that represent the configuration I have.
The two center tanks (center, center2) were standard, but the optionall Center3 tank was larger, and was only used when no bomb load was needed.
The ferry tank is the external, droppable tank. It could be used with a bomb load (without the center3 tank) although there is no record of that ever happening.
In FS9, the way the load sheet works is you can have the ferry tank and the center3 tank loaded together.
If you have bombs or torpedo or a belly cannon pod, the ferry tank and center3 is not available, and vice versa.
In terms of fuel feed, I have now forgotten how the center tanks work and will have to do some reading.
I believe they are all in-line serial feeds, one through the other, but will verify.
EDIT: I am attaching a zip file of these screenshots, larger and better to view.