I grew up in a place where 99.9% of the roads were dirt. Most of the time I had a two wheel drive truck. I got around a lot and it was some work, but it is doable. I used chains a lot. A Hi Lift jack with chain and hooks is awesome and a must-have; they aren't dangerous if you use them correctly. Four wheel drive is nice, but it is expensive. Having a chainsaw is quite helpful, too, but not practical for a vandweller. Use a good spare and keep air in it. Lowering air pressure in the tires works amazingly well. Take one of those 12 volt air compressors with you. Take two! They're cheap. Bob has some recommendations for that somewhere on this site.
I would totally do Gross Reservoir in a two wheel drive without lockers when it is dry. You usually don't need a lift to put tires on that are a little bigger. I've always used stock tire size and it hasn't stopped me. I literally can't think of a time clearance was an issue for me, but I don't try to "four wheel". I just like to get to the cool places to hike or camp. I'm not into the stuff you see on TV. Larger tires are harder on the transmission/clutch and brakes so be aware of that extra cost.
Lockers are awesome, too. That will set you back around $700 or so. Lots cheaper than four wheel drive and no maintenance if you get the Torsion style locker. You can easily spend $1500 for lockers that are air or electric actuated.
I saw a Sprinter van today that was two wheel drive. The roof rack had a spare tire, at least two aluminum traction ramp thingys, larger tires, a winch on the front, and not sure what else. He was camping beside the road near Glacier National Park. I should have taken the time to stop and visit. I could've learned something. If he's there tomorrow, I won't be such a wuss and will stop.
I had purchased a 4X4 van, but it didn't work out. I'm glad it didn't because the parts to make it 4X4 are largely proprietary. Have fun finding parts for it and if you do find parts for an old van, have fun being able to afford it. You think 4X4 on a truck is expensive? Try a 4X4 van. Some parts are the same as a truck, but the mounts and tie rods can be a bugger.
A year ago I took my two wheel drive truck for a drive. Went down a road that was 21% grade. I knew that was steep, but since there were no other warning signs such as "4X4 only!", I went for it. Ended up breaking both motor mounts and the transmission mount driving out. $100 (maybe more. Can't remember) dollars in parts and about 10 hours of hard labor to replace it. This wasn't a trail, either. This maintain gravel road led to the river and was a boat launch to a popular fishing access site. Going where few go in a two wheel drive is fun, but be prepared. I do it all the time and rarely regret it; I usually know my limitations. I see lots of places in my S10. When I'm worried about where I'm going I drive the F250 4X4. I have no desire for rock crawling, so 4X4 gets me almost anywhere I desire. Heavy rains, flooding, wash outs, other people stuck in the road, or people that have hopelessly torn up the road, and the like are about the only things that stop me.
I've helped get a lot of people unstuck, but that gets old especially when they are drunk or otherwise being stupid. I'm OK with kids doing dumb things because that's how you learn, but the doofus adults try my patience. Most of the time they don't stop and get help, but bury themselves up to the axles making getting unstuck way, way harder. Sometimes I've been pulling them out and they keep digging and keep getting themselves stuck instead of letting me pull them out. Kind of part of the deal, though, because if I ever need help, I NEED help and don't ever want to be turned away.
Learn your equipment before getting out there!!! Put your chains on and off a few times. Use your method of winching yourself out a few times. Keep stuff lubed. Getting stuck sucks, but not knowing how to use your equipment or not maintaining it is really aggravating. I've neglected my stuff and paid the price a few times!
