If you're 5'10", then with the rear seat cushions removed (very easy to do), you will fit no problem. Get those winged nuts that doubledown is talking about and it will make the removal that much easier. However, there is a tiny bit of height difference between the rear cargo area and the rear seats, when folded down, so you will have to lay down some foam or build a sleeping platform if you want to be comfortable.
If you can do it with the size of the 4Runner, I say go for that. 3.4L V6's in the 3rd Gen 4Runners are stout engines and will get 20+ MPG on the freeway stock.