You might consider a Toyota E-Locker.

There are some deals out there. I bought mine factory new, in the box, to my door for $385.00.
The only bad thing is it has 3.90's and I want 4.56's, but for $385 I'm not complaining.

For the front I would consider a Detroit True Trac. From what people tell me you don't even know it's there when your steering. The only bad thing is if you have a tire off the ground you have to step slightly on the brake to keep it from spinning. They work great as long as both tires are on the ground.