Ok here's what i'm thinking.
make it look similar to this
make it 7 high, 36 wide, and 16 deep.
single 4" port firing off to the side in the wheel well
i accounted for .1 bracing displacement, so throw a 4 1/4" wide by 34.5" long 45 degree piece running the entire width along the bottom/back of the box (as seen in the picture)
you're tuned to 32hz with 10 inches per cube.
if you wanted to get a little more port area, you could do a pair of 3" ports rather than a single 4. same length would tune you to 34, but should still hit the lows nicely