My son has a regular cab 97 Ranger and we built a dual 10 box that fit behind the seats. We divided the box in 3 sections (center section about 9" wide) and put the amp in the middle. It sounded like crap. The speakers distorted badly at only moderate volume levels. Enclosures just not big enough.
We're going to try 8" subs next and see if they work any better. If not, we'll have to redesign the box and find another spot for the amp. Those reg cabs are small
p.s. Our box measures 13" high, 3.5" at the top, 6.5" at the bottom and 36" long. Took out the tire jack and clip. The box just fits under the lip on the back wall and the seats are one click from full back.
1999 Buick Park Ave Ultra
Head Unit: JVC KWHDR720
EQ: Audiocontrol EQL
Front Stage: Hybrid Audio Technologies Imagine 5.25 mids, Morel Maximo tweets
Sub Stage: Boston G3 10", 0.5 cu ft sealed
Amp: PPI Phantom 900.4
Rear Fill: Boston SE953 6X9's