new storage Idea 95 Reg cab, I came up with while in the shower

So, I do my best (or worst) thinking while in the shower.
Get the mental image out of your heads you pervs.

anyway, My bed is rotting away, and I am drawing up some plans for a flat bed. I also am wanting some storage area inside the cab though for sub-woofer, amp and a gun safe.

Since I am nixing the factory bed, I am thinking of building a small 6-12" bump out behind the seats. Maybe 12" tall too?
On the Flat bed I was going to incorporate a store bought tool box at the fron of the bed which leaves a small bit of unused space below it. So I was thinking that space could be turned into storage inside the cab. It would be a lot of fabricating, but would be fun to figure out how to make it work.

thoughts?