I drive an fzj80 and love it. It's also my daily driver. If you plan to primarily do overlanding with limited rocks and medium trails, 100 is the way to go. V8 power is nice and the IFS is pretty good. Get one with the locking rear diffy and you'll have a pretty solid rig. Upgrade the front suspension a little and you'll have a very capable rig. I built mine to handle both. I can do Death Valley type runs, hit the Rubicon and everything in between. I wanted to get it right the first time and not have to rebuild it as I go. Thats why I kinda overbuilt it. Just think about what you really want to do with your rig. The 80's are great with bullet proof engines (almost 250K miles!), solid axles and optional f/r lockers. Just plan on not getting anywhere in a hurry. Also, they don't hills, like, at all. 100 will be smooth on the highway and get ya where you need to go with gusto. Solid platform to build on. Won't be doing any hard rock crawling with this one, though. IFS not quite up to the task. '98 and '99 came with the rear locker option. You can get 100 series cheaper than an 80 series now! Yea, go figure. Lexus version even cheaper than Toyota since people want the Land Cruiser name.
I'm with 1derer on the diesel option. Not really needed unless you plan to go on all kinds of international destinations with it. Good luck with the purchase/build.