There are a couple of ways to go
1) Buy the off-road version of a new pop-up. Most feel they aren't super tough but they are better than stock PUPs.
Here is a site where some folks start with a pretty nice stock off-road PUP
2) Buy an old one and spend a lot of time and some money making it custom. To get something that rides even with an 01 XJ with a lifts and 31' tires that's likely what you'll need to do.
Here are some examples:
-The first is mine. It's not very good but I try hard. I have a 2001 Jeep Cherokee with a 2" lift and 31" tires. I bought an old Starcraft camper and ended up tearing it down to the frame. Thread link
here
-The second is psychosquirrel's. He found an old apache tent camper and is customizing it. KILLER build, but it won't be AC friendly. Thread link
here
-Third is a great build by Jet noise. He got a Coleman Colorado and spruced it up (also not likely to be AC friendly- you need a hard roof for traditional AC) Thread link
here
-Texas TJ also has a nce Coleman Colorado build thread
here
-Atoyot has one of the king-daddy of all builds. The pics have expired on some threads, but I found it on mud. Thread link
here
Another cool option could be something like the Adrenalin posted
here not a classic PUP but awesome.
OK, I've been researching this for almost 2 years and you just saved yourself months of looking on-line if you looked at that collection of threads. I only posted threads that were either done or near-funcitonal. A LOT of them have stalled out in the halfway done phase.
As far as which brand PUP and what you find, I'm happy to offer my opinion, for instance, I would choose a Coleman over Starcraft knowing what I know now about how the frame and lift system is integrated.
Good luck.
Thom