i just installed my single 1200 watt 12" sony xplod into my wheel well. a sweet set up. heres a step by step. (not sure if u can throw 2 in there, but i think its a possibility.)
1) u are gonna have to grind off the small spare tire mount in the floor.
2) i took my woofer box and cut the front of it off, then re-mounted the sub in that thin front piece. the bottom of the woofer hangs out the back a little.
3)stuff some foam around behind the sub and staple it into the box so you dont any nasty rattles and have a bigger, better thump.
4) i then attached two small 2x4's to the bottom of the box (the part i had cut, it has the sub in it) to keep the sub off the floor when you put the box down.
5) now i didnt bolt it down to the floor, but here is what i DID do: i centered the sub in the wheel well. then i took two cans of Great Stuff and sprayed it around the box, between it and the wheel well. Great Stuff is foam insulation in a can, and it dries VERY hard. two cans gave me about a 4"x5" ring all the way around the woofer box. trust me, that puppy aint goin NOWHERE, lol. i was really impressed with how it turned out.
6) as far as how to finish, you have a few options -- i just painted the foam bright red, since no one is gonna see it. you could frame the box in wood, and run the wood to the sides of your trunk. or you could carpet the foam. there are a lot of options.
ill post up pics so you can get an idea of what it looks like. the thump is solid, and the sub isnt gonna break loose anytime soon.