As for the 3 subs in the sibgle box it is doable, I think I actually crammed 5 behind your seat with AutoCad but thats borderline doable. Here are your options at least when it comes to wirering up the subs. This should help you in finding an amp as the ohm load that the amp is stable to will be part of the equation.
With this try to find a 1ohm stable amp that may do a little over the rating for the subs.
and according to
Crutchfield you could do this
Crutchfield Wirering Diagram
Or if you stick with 2 subs you can do either or...
Of course here the 2ohm load would be recomended versus the 8ohm load. But those should be your options. Of course there are more with different subs configurations and such but thats what you could do with the kickers you picked and either 2 or 3 sub config.
With the two subs you may be able to get away with ported but I am not too experienced with designing ported boxes, specially for regular cab trucks tucked behind the seat.
As for the components I would say mount the mid in the door in the factory location (making a trim ring of course to adapt it to the 6x8 hole. Then mount the tweeter somewhere on the door, maybe squeeze it in under the panel next to the other speaker, or maybe flush mount it up where the panel covers the side view mirror mounts, something like this...
