I cant speak to the available room, but not only that, you should consider the SEATS themselves. I know in the Tundra AC, the rear seats are pretty basic, and would probably get uncomfortable pretty quickly...Short, sub-1hr, trips may be OK, but anything longer would probably push it. The AC seat backs are basically just a couple degrees off upright. There is a mod that is popular, where you use spacers to kick out the bottom of it, to help with the angle, but I think you only get maybe another couple degrees or so.
Plus, the seat foams (back and bottoms), are pretty thin, and especially FLAT, and harder due to less room behind/under the seats themselves for the cushions to expand back/down to mold more to a persons body, before bottoming out at the back wall, or the storage space underneath.
Also, there is absolutely ZERO adjustment on the AC seats...everything is hard-bolted in place....Not sure if DCs have any or not...
As to pics of the seats themselves, (MAYBE with some poeple...lol), just Google "2001 Tundra rear seat", then click Images under the search box, and notice the 90° between the seat back and bottom...Then just think of sitting upright like that in the SAME position for over an hour...lol