DML FAQ : Stereo : What are the best locations for two 10's or one 12 subwoofer in a GenIII Reg Cab?
That might be a little too tight. Depends on the size of the passengers really. I went with a high quality 10" Infinity Perfect series sub behind the passenger seat and mounted the amp behind the drivers seat. That setup takes up the majority of my extra space. BTW, I also had to remove the jack to fit the sub.