Tell us any specs you can on the subs, like parameters or atleast what motor and soft parts Ssacket is using for the subs... also, how do you plan on using them (daily, sq, spl)?
Rough estimate, since I don't know your trunk height or sub displacement...
External dimensions: 16" height x 32" width x 18" depth, using 3/4 mdf
Port: 3" slot port vertically on the back side of the box, to either side of the subs. Port will be 30" long, so it will be L shaped, and finish in the back center of the box. This will give a tuning freq of 35 Hz.
Give more info, and I might be able to help more.