Wow, i miss this discussion until today!
A few points:
1. If you're going to get FJ80, then i would find one with front and rear lockers. Unfortunately, only about 10-15% of FJ80 (and LX450)that came to the US had them...so, they are extremely hard to find since most of them are bought already by enthusiasts. Otherwise, a FJ80 withOUT lockers is OK, but may not be worth the money.
2. 4Runners are excellent value vehicles. However, they are more of a daily all-around vehicle.
3. For YOUR needs, i would get something that is capable, yet easily modifiable in the future with lifts and winches and big tires. For this, i would recommend a Jeep Wrangler. It is cheap, cheap to maintain, and it's aftermarket support is unrivaled, bar none.
4. Discovery Series II is junk IMHO. My brother had one...a pure maintainence nightmare. Off-road, it was good with A-TRAC (4-wheel traction control). However, to fit lockers, you need to UPGRADE axles and CV joints!! Stock axles are relatively weak and canNOT handle the stress of lockers. Thus, most LR owners who install lockers also upgrade their axles. If it doesn't leak, then there is something wrong with the LR!

Rust is also a major issue with LR, even with all their aluminum parts...don't ask me why, but it is a common problem. I think that their aluminum parts are of the low quality impure variety...not the aluminum found in Jaguar vehicles.
Again, a 4runner is a good vehicle...but it seems like you need something that can be modded easily and cheaply. If you can find a FJ80 with lockers, then buy one immediately...but make damn sure that it has not been "abused" by a fellow enthusiast.
Good luck in your search.