I've seen (and installed) lots of reg cab rangers & s-10's with 4 regular depth 10" subs behind the seat.
It depends on the subs you choose. If you were to use a $500 competition sub, you'd probably need 12" or more of mounting depth. On the other hand, if you used something like a RF, MTX, Pioneer, etc. mid price range sub, you may only need 5" to 6" of mounting depth.
If you can find conventional subs that have a mounting depth that's shallow enough, you're good to go & they'll probably be cheaper than the shallow subs too.
You might want to take a look over @ crutchfield & compare mounting depths & box volume requirements before making up your mind.
Hope this helps