need help designing a blow thru DD 9515Z's

[swervinburban]

well like the title says I need some help designing a blow thru box in a 96 nissan pickup. I currently have 2 dd 9515z'S, but if its possible to fit 3 I will buy another one and run 3 of them. My wall was 10^3 and peaked at 43Hz I would like it to peak a lil lower since most of the music I listen to is low and I been killing my subs on the low notes. I personally think that 5^3 per sub is to big for the amount of power im runnig but I may be wrong. Im sending one sub off for a recone this week and im thinking this is a perfect time for a rebuild. If need be the box can feel up the whole bed of the truck, but I would like to leave enough room to run a battery bank all the way to the rear of the bed. The dimensions of the bed in between the fender welds are height 16", width 40", and length 70". If needed be the box can go around the fender welds which will give a width of 48" and I can fiber glass the fender welds. Any other mesurements can be taken if needed. Ohh these measurements were taken with one of those plastic bed liners in it so the may be off by an inch I'll take it out tomorrow and remeasure everything but atleast you have an idea about how much room I have in the back Thanks for the help in advance