trying to do a sealed setup? iirc you can build the box to where the seats lay down and have the seat sit above the subs which would be placed on left and right side of box, and amp in the middle. my buddy did this design. if i can get ahold of him ill shoot oyu at least a pic of that box. but if you want to do a sealed setup there should be no problem at all.
if anything just figure how tall the box can be and find your internal volume, minus sub displacement, bam youre done lol. tuning is what i dont know how to calc on paper