Does anyone know how many ft^3 of space is in our tire well? I want to put my subs in there as I am sick of have no space in my hatch and don't what to rip out the system to find out there isn't enough space.
Also does anyone know approx. how many gallons of resin it takes to make a enclosure to fit in there? Thanks for your help.

My enclosure for two 10's is roughly 1.5 cubic feet according to the guy that made it. You can see pics here: http://stereoinstall.importvenom.com

I just did this earlier this week. I didn't build a box though. I sand-blasted the whole enclosure area, then mar-glassed it, then sanded it smooth. I made sure to leave enough on top, so my false floor would butt up to it. Then I used a VERY thin layer of expanda-foam all around the well (not in it) and put my floor down while it was still wet, and before it expanded, and bolted it down. It is sealed tight, and sounds great.
These enclosures sound better than boxes IMHO because the false floor essentially becomes part of the car once bolted down. You also get 99.9% of your trunk space too!!!

I have a box in my spare tire well, or at least I used to, which is 2.26 cubic feet. I can even mount my battery in the extra area.

If you are trying to measure out the air space in your box, provided it is fiberglass, fill it with water. Drill a small hole in the bottom and measure how many gallons of water you remove. Do some math and convert it to cubic feet.

And I never thought that I would have used Geometry!