The v8's only get an mpg or 2 less than the I6's.
I have a 4.0 in my zj, it's a great motor but sometimes I wish it had more power. If I could do it again I'd get a v8.
That is accurate in the ZJ, but in the WJ the V-8 actually gets Better mileage than the I-6 (as I believe I stated earlier.)
The runner. Well, I like the older runners, the 90's models, but the new ones are just UGLY!
If you had the cash your best bet would be to go with the NEW Grands that are coming out soon. Those things are amazing right out of the box, they do everything you would ever need in an easy trail/dd jeep. PLUS you have the added bonus of not having the truck drive itself into things like the Toyotas.
(personally I would never buy another toyota for the simple reason that they are tiny inside. Sure sure they have tons of cubby holes, but if you can not drive the thing what is the point!? Then again I am 6'5, but talk about no leg room.)
I would also get into the back of them and check out how you fit back there. Not that you will ever have to, but I should think that it would be nice to know if someone our size or larger would be comfortable back there with the seat where you like to put it.
Good luck then.