Here is a box that I did for a friend of mine in a regular cab S-10. It is really thin (the seat is only 1 notch forward from being all the way back). It has .5^f per chamber, which is the minimum air space requirements for the 12" shallow mount. It is not the loudest, but it has a very clean punchy sound.
Here is one for 4 10" subs in an S-10. It has 4 chambers and each chamber has .66^f. This guy pretty much eats the dash, but it is what he wanted.