Box for 2 Sundown X-8 V.2 subs?

[Farmer6.7]

I am looking for help designing a box for an extended cab F-250. I am wanting to go with 2 Sundown X8's on either a Rockford T1500BDCP or a Sundown SAE 1500... 

If the x8's don't have much to offer over the SA 8 v.3 maybe I could go that route on a t1001bcd or a SAE 1000... also maybe a slightly smaller box. But if the x8's offer the same sound quality and slightly more SPL I would want to go that route... 

Box would need an internal volume of 1.5 cubes after sub displacement. I want to tune to 31-33 hz.... I can build a box if I have blue prints, but in terms of figuring port size for tuning and subwoofer displacement I get lost. 

The dimensions I am willing to work with are 32" Wide, 18" High, and 12" Deep, I have attached a picture showing the max dimensions I can do. I cannot remove the seat cushion... that was my initial plan but it is not possible without removing the single seat on the drivers side as well. 

 

Some other concerns I have are if this will even sound good in an extended cab truck, it has been about 7-8 years since I have had any bass, previously I have had anything from 1 10" w7 to 2 15" t2's... in a Ford Explorer. I have fears the extended cab truck will sound bad or there will be port noise or storage sounds as I will be so close to the subs and port will be close to obstacles. I read forward firing is best in trucks.... 

Another concern is if my electrical would handle 1500+ watts... my truck is a 2011 F-250 Diesel so it has a pretty big alternator for a stock vehicle as well as 2 batteries.. I would have big 3 done so surely I would be okay?

 

Thank you for any advice, input, or box designs.... I am willing to pay for a properly designed set of box blueprints that are straight forward. 

[Farmer6.7]

One other idea running through my mind.. since the SA V.3 8" calls for a slightly smaller space I wonder about doing 3 SA v.3's on one of the two mentioned 1500 watt amps? Fair bit more cone area that way... any thoughts?