What year truck? I have one I built (and removed) for my personal 2010 F250 regular cab. It will fit 2008-2012 regular cab Super Duties. Its built for a single Pioneer or Rockford Fosgate shallow 12".
im running two db drive 12" subs, 750 rms a piece one behind each seat, ones ported the other is sealed, sounds great and has a really full sound. those were the biggest subs i could fit, had to modify the box a bit even.