Box Design For 4 12s

[cooneytay]

Basically I want a box that looks like this:

I know how to calculate the square foot and everything but I am not sure exactly how ports work and using it with the speaker box tuning calculator. I was wondering if somebody could help me out with a box design for four 12" subs. The manufacturer recommends 1.75 cubic foot for each sub. Mac dimensions are roughly 40" tall, about 18" deep, and as wide as it needs to be. Also, I would like it tuned to about 33hz. It is going in the back of my gmc canyon after I remove the rear seat. The subs are Pioneer TS-W303R, I know they are not the best subs but I know how I can get my hands on two more for really cheap because I already have two. If someone can show me a good design then I can offer money but I am not looking to pay a whole lot being that this box and woofer set up isn't exactly final. Even if you could explain a little how pots work I would greatly appreciate it.