I'll chime in on the Xterrs as well. Great platform. I had the frontier crew. Loved it, wish I still had it. Was going to trade it on an Xterra(wife was driving it more, etc). Been wheeling with a bunch of them. Plenty capable. Get on the highway, and you should be able to get close to 20mpg. I broke 20 a couple times(hand calc'd avg) on some longer trips. Got about 16 towing my trailer from Mass to Texas. I wouldn't have had as much of a hit with a cap, or the Xterra. Good parts availability. Need to be careful about year, etc with an automatic. Get service history. The trans cooler in the earlier models, was prone to cracking, and would get coolant into the transmission.(strawberry milkshake referenced above). Th radiator can be bypassed easy and cheap, takes longer to get the skid plate down... Most have an external cooler.
Montero, another good choice.
Trooper, very capable, will take a lot of abuse, can be found with a manual transmission, and HUGE inside. Parts availability is getting scarce, which is also driving the price DOWN.
Tahoe, good full size platform, decent clearance in stock form, lots of room, reliable drivetrain, with all but unlimited parts availability.
Jeep, well, budget and needs will dictate. I'm running a WJ now, last of the solid axles. We have 3 kids, and this is the minimum amount of room I'd go with. This is riding on a Clayton, axle work, etc. gets between 12-15mpg, but, I live in the city, and about 1/3-1/2 of the driving I on the beach. Parts availability, it's a Jeep.
Sounds like what you need is a full size, crew cab, diesel. You can get an OBS Powerstroke in that range. 7.3 may not be the most powerful thing out there, but, it's reliable. More modern crew diesel, figure 2-3 times your budget(particularly for a Cummins). Cummins will net you the best mileage, but, will be the highest cost.
Land Cruiser. I love them. But, 5-10k for a LC with 100-300k on it, no thank you. Eye usually fetch a ridiculous premium. And not all of them are worth it.
There are tons of vehicles out there....
I've been looking for an old FSJ, to go back to simple, and easy......
Good luck. Have fun with the build.
Chase