need measurements for behind the seat speaker cabinet

[snipescastle2]

Hello everyone! I would like to ask a favor from anyone who can take a few measurements for me, since my cab is out for paint right now.
I need to know the height from the area of the cab floor (where stock gas tank was) to the area
Directly under the area where the top of the stock fuel tank was (under the painted curved cab wall is) that should do it for now. Thanks!
Ben Smith