Thank you, I run E85 in my turbo GTO so I would also like a big tank to carry the fuel for my E85 barracuda turbo build also! Thanks for the info. You have really thought ahead, I would have never thought about raising the floor to hide electronics
If you measure the hump where the rear shocks bolt in it is about 4" taller than the floor behind it. The in tank fuel pump sits in a recess that sits flush with the existing floor, that makes it 4" lower than the surrounding tank. Now I can make aluminum panels held in place with dzus fasteners to create a floor with several compartments. Use some simple aluminum C-channel bolted to the floor around the perimeter and a few other spots to act as supports. Put some dynamat on top and some carpet. Simple, clean, and will also function as a firewall between the fuel system and the passenger compartment. I have not decided yet where I will put the fuel filter, but it may not be an issue for it to be between the tank and the shock mounts.
The trunk will still be plenty big enough that I can put a spare. I will get a reasonably sized "space saver" make a mount for it, and put a cover on it.
A battery is about 8" tall. So I would make a pocket for it to sit in on the far right. May or may not hide it.