Does anyone have or know where I can find the dimensions of the space under the rear seat of a 99 ext cab? Looking for ideas for a box.

 

Are you looking to build your own box or buy one? 10 or 12/single or double?

Whether you're buying or building check out these boxes:

http://www.foxacoustics.com/ProductD...150%2D210%2D00

This has dimensions:
http://cgi.ebay.com/FORD-F150-12-EXT...item483b3db010

Also check this out it might help you with the seat, because i'm pretty sure you're gonna need a seat lift. Trust me its not that hard i've done it 3 times. (You don't have to take out the middle bracket if you find the right box)

http://www.fordf150.net/howto/subbox.php