The factory sub enclose is far from regularly shaped. I just measured mine and it is about 13x13x3...of course it is much larger than that, but has many areas that are less than 3" deep. I cannot say if it will fit or not but it would be close. The cover will flex a bit to help you and the seat will hide said flex. I am sure they have a return policy so give it a try and let us know. Do you have an aftermarket head unit or planning to connect to factory radio?
09 G8GT, Stryker, sport/prem
08 GXP, Mean, Auto
03 Excursion Limited, V10, 2WD and 37s
94 Bronco XLT, 5.8L, very rusty and 35s
07 GXP, Mean, manual-RIP 1Apr13 @14K miles