I'll agree with most that its worth buying a built rig and just go wheeling. I've spent a ton of time and money building my crawler.
Not sure I would qualfy the FJ80 axles as "1 ton". Yes, the rear is full float, but its uses a 9.5" ring and pinion but is much small then a Dana 60/Sterling/14 Bolt. That said, its plenty strong and can be found with an elocker. The front is definitely not a 1 ton, as it uses the same 8" ring and pinion size as the 4runner's and Pickup's, just in high pinion instead of low/mid.
There are options beyond finding a donor axle, and its a good way to go these days. If you are going to SAS something and want it to be easy, as much as I'm not a fan of everything they do Trail Gear has some good SAS kits for various years of 4runner. Some of them come with absolutely everything you need including a fully built axle and suspension and the stuff to retrofit.
IMHO though, unless you are set on big tires and want to get full offroad performance, adding some upper a-arms and getting good shocks to match goes a long ways towards making it a very capable vehicle without having to sacrifice on road handling. If you go 1st gen 4runner too, there are some cheap ways to do a Long travel independent suspension too. That is the route I'm probably going to go with my "spare parts" rig.
Lots of tradeoffs in this world....just gotta figure out which ones are important to you.