box building tips needed

Im an installer not a carpenter. Pre fab boxes are so cheap and well built I havent had to build anything in years. I can whip out a sealed box with no problem but i cant remember how to get all the ported info.

I am doing a custom box build in a 69 fastback using 2 Alpine swr-1042D subwoofers. i have been on a few sites trying to figure out port area, length, volume, tuning frequency...blah blah blah. its all to damn confusing now. I have 1.8 cubic feet of net volume that is usable. Ported volume minimum is .7 cubic feet. two makes 1.4. I figure i will invert the subs to leave plenty of room in the box for the port. now i just need to figure out what the port size will be. I would like to use a square port thinking it would look better but everything converts for a round port. can someone help me get my head wrapped around this BS before i go nuts?

thanks for the quick responce. i have been trying to talk this guy into a sealed enclosure for a week or two now. He designed a ported box where the ports were on the opposite side as the sub. i told him i wont do it and now he is wized. i figured i build him his ported box to "specs" using my expertise in this area. I may not be the best builder but i know what should and should not be done.

If he really wants this ported box i will have to build it in the car. where as the sealed box can be built in the shop and secured in place in the car. i can build panels to make it all blend and look like a show car, but he doesnt wanna hear it. if he was a customer id tell him to hit the road. but its the owner of the shop so i gotta do what he wants. F it! im getting paid either way