All I ever see people do on F-bodies is the dual 12" subs that take up the whole hatch. I'm not looking to go that nuts and I'm leaning towards 1 10" that would go where the spare tire is. I haven't seen anyone do this yet. Has anyone done it, and if so, what does it look like and do you have any dimensions to reproduce another box?

Its been done before. I've also seen a box that puts a 12 in the glove compartment.
I dont know the numbers but a tape measure should help you out.
BTW normally boxes like these are made out of fiberglass. but this one isnt. https://www.thirdgen.org/techbb2/sho...e+tire+sub+box