Re: How big a box do i need and does it fit?
You'd be better off with tens or eights, so you can keep a rear firing enclosure. A single twelve might work. Just get something beefy, a nice box design, and throw gobs if power at it.
SoundQubed 6.5 Pro's DD T2 Tweeters / Phoenix Gold Xenon 100.4
FI SP4 15 D1 w/ Tantric Sounds softies / DC 5.0K
Singer 310 6 phase 2 runs of Monster Cable 1/0 / Exide g78 AGM under hood and XS D3100 in rear
Plenty of deadener. CCF and fiberglass insulation in doors... thanks to the advice of keep_hope_alive they sound AWESOME! :-)