BigH8840

So i've been looking to upgrade my sound in the truck and I seeking a little advice. First off, would I have enough room to build a custom box (unless someone makes it) behind the back seat. I know I would have to remove the seats for install but figured i would have enough room for 2-4 shallow mount 10" subs. I don't wanna use the under the seat box because I use the inside of the cab a lot to haul some stuff.
The other thing I was looking at other than new speakers all around is to upgrade the factory single cd unit. Is a standard double din conversion going to allow me to use most dd units? What about putting in the factory unit that is the touchscreen model?

GATORB8

I doubt you will fit anything behind the backseat, you've only got a couple inches at the deepest location.

There are double din dash kits available.