Tundra should work fine, but watch the payload. Make sure the timing belt has been changed in the last 90k miles as well.
I mentioned this in another thread, but if I were single, no kids, I'd probably get a 1/2 ton RCSB. XL or Tradesman, 4WD, V8, 3.73 locked rear, ICON susp, 33's, and a high-rise shell. Big enough on the inside for single (or +1) travel, comfortable than midsize for long road days, and small enough for most trails.
I'd probably not build out the inside of the shell. Keep it simple with a cot or mattress that can quickly be removed. Typical payload is 1,700lbs (or more), so unless you're doing some heavy hauling or towing, it should be fine.
Like this, except high-rise shell (ie, ARE MX).
View attachment 572342
Someone mentioned vans. They're nice and all, but no way I'd opt for one, given the OP's driving terrain. Sprinters suck off road. Yes, you can get 4WD E-series vans, but those are clobbered together, which means servicing them would be a pain. I'd keep it simple and keep it as OEM as much as possible for parts availability and serviceability.