help designing a box

[Hertz_dont_it]

ok im going to do a blow through on my 1991 s-10 standard cab. my idea was to make a box kind of like a bandpass but instead of usin plexi glass i was going to use wood and i want the subs facing the tailgate but ofcourse since its like a bandpass the subs are inside and i want there to be port a port or ports if i have to but i was going to do one port and have it run into the cab because i was goin to cut a hole in the bed and in the back of the cab and run the port through. but i would like someone to sketch it up for me usin google sketchup or somethin like that, i havent decided what subs im gonna use yet or size. dimensions are, from the front of the bed(where the cab and bed meet) to the wheel wells are 21" from front to wheel well and 56" from side to side but i want to leave room from side to side so that i can put stuff beside it. so i was thinkin anywhere from 7-10" on each side. on subs though i was thinkin either 3 12's (i have measured that out and i can fit 3 12's if i extend the box to 40") or 2 15's. i just need some ideas and sketchups please and thanks