2 x 15s in a van.

Hey there, I am looking for some sort of guidance on what I should do with my... project. I have a 2000 E250 work van. Its going to be, if it isnt already, a creeper van. I started this with the intention of a basic stereo and it has grown. I wanted to do everything CHEAP. Which hasnt really happened'ish. I want it LOUD. Current issue is the Subs. I just purchased PrecisionPower P15 D2's I am going to be powering them with the Hifonics Brutus 3016 Everything is going to be wired at 2 ohms. So I figure I will have the gain down to make sure I dont blow everything the first day. Problem 1) I was trying to figure out what I needed for the box - I tried WinISD but there isnt a listing for the particular speakers. I then attempted to input the information off of the "Specifications" tab on the manufactures website, and I got lost This isnt what I do and Im guessing some of the figures were either not provided or labeled differently. I couldnt find, what seems to be, important data for WinISD. Im I missing something or is the information called something differently. Problem 2) I want to go with a ported box. Though I am lost on trying to design the box(Horrible at Sketchup.) Building it - I have that covered. Is there a program, that will allow one to pick options and then develops a cut list for specific designs? Could someone point me in a direction? I can make a simple sealed box - I can do the math and get the ideal internal volume, but I start to get lost when it comes to the ports and if they are calculated into the volume or removed from; where they should go, middle, outside, etc.; what frequency its "tuned" for and really what that all means. Problem 3) Where should I put the box. The entire cargo section of the van is open. It does have a "work barrier" separating the front cabin from the rear. It has a door, which I was thinking of removing. Where can I get the best "bass" for the buck? If I fire the speakers/port into the cabin or if I place them on the side of the van. I could face the speakers to the rear and the port to the front - That would mean I have nearly 10 linear ft of open air from the subs to the rear door. I would like to stay away from putting the speakers in the rear and firing forward as that would make usability difficult. Problem 4) How beefy do I need to make my Van - Do I need to buy more batteries. I am waiting for the main to die before I buy a new yellow top. At this point I am planning on 2 additional batteries sealed along with the upgraded standard. I worry about the alternator with that much draw. Should I do the batteries or the alternator 1st. I had wanted to simply add a second alternator but finding the bracket is proving more than difficult. I just dont know what I want to get first - batteries or Alternator. Any help with this will be greatly appreciated. John