Well you have plenty of power from amps, hoPefully you have the electrical to back it up, if so, instead of guessing on a box size, like I have, there's a couple of ways you can go about this.
If you're looking just for a daily pounding setup, build it around 2.2-2.5ft3 per sub
If you're looking for it to meter well, ie competition, then start the box at 5ft3 and add wood to it until you find what size of box the subs like.
Tuning to 34hz will definitely be a low hitter.
Remember, if you build a box that is too big, you can always cut it down, especially since you're going with aero ports.
The sad part is, every car is different and subs sound different in different sizes. But I would start at 5ft3 and go from there. Good luck with the build man