I added a single 1x4 brace for the hell of it. You don't have to put it in there. That was just cause I felt like it.
I flush mounted the subs for you. From the pics I could find, the box should fit with some room to spare.
Anyway, the subs will be a little close to the walls. You'll have to be carefull cutting the holes.
The center of the holes are exactly 6 inches from the side walls and centered between the fron and back walls.
The box can be faced up, back, or forward.
I'm about to finish it now.
EDIT: what color is the car?
EDIT EDIT:
Here the box is carpeted. The Toyota Celica is just a little extra touch.