early to mid 90"s 4x4 suburban is your best choice, Tons of room in the back.
Guys here on the gulf coast use them for week long fishing trips.
Buy a honda "quiet" generator and a window Rv roof mounted AC. Geet a full length roof basket, mounted up on thin rubber isolators. then mount thr Ac and gennie on rubber isolators and you will never know they are on.
Plump the Fuel for the gennie into one of the 2 massive 25 gallon fuel tanks and you are good to go..
Paint rear glass black on inside then cover it with dynomat and the sun wont bother you in the mornin, aswell as it will keep the Sleeping area nice and cool all day long.
As for sleeping, look for aluminum framed cots, remove the legs and bolt them to the innder body of the burban with hinges so they can be folded up when not in use. if done correctly, you can mount two on each side if you chose too.
If you wanted to go all out, get a headliner mounted fold down display and mount it up in venter for some Tv or movie late nights...
Theres some awesome Rigs that cruise up and down PINS here in texas..
These guys sleep like kings in these Burbans..
you can buy and rig completly one out including MPG mods for cheaper than you can buy a decent 2000+ Tahoe.