[elhigh]

If you aren't mudding or going after serious slick rock trails, you might not need to 4x4 capability. A well-sorted 4x2 can get you very far afield. A couple of extra inches of lift, a couple of extra inches of tire and a locking diff or a good limited-slip diff can work wonders. Look at all those VW sandrails and rock buggies that get so far out in the wild, they do okay with only two wheels driving.

I think the important bits are to keep your CG low, keep the suspension soft and long to keep the tires on the ground (a switchable antiroll bar is good for this), and shed as much weight as you can. The less mass you tote around, the less traction you need to shift it. If you can add an overdrive (pricey) to slow down the driveline on the trail, that'd be nice. Add a sacrificial airdam (you know you're going to leave it on a root or something) to minimize the wind underneath and off you go.

Really though I think your best bet is what the other guy said: for towing and highway use, you can do well with a nice vehicle that gets good mileage. And when you have to go blazing trails in the backwoods, dig out Ol' Crusty and don't worry about the MPGs quite so much.