Brent,
I have a SW in my westy.  It is in a smallish box on its own,  which I sit behind the passenger seat on the floor.  I got the Box at CarToys (local stereo dealer) for about $20.  It's wide and tall but thin and the speaker points to the rear on a sloped face.  IE the dimension away from the battery box (into the floor space) is only about four inches.  It is just about the same width as the battery box and maybe an inch taller.  Its covered with the standard speaker box/auto carpet (grey).  I ran wires to it with stereo jacks so I can remove it.  It's cheap, fits well, removable, but is definitely not the "optimum" size for the speaker. 
Nat 
Seattle