I've had an auto locker in the back of a couple different trucks. No issues at all driving on wet roads. Only got a little dodgy in snow and ice, but still liveable if you're really paying attention to what you're doing. I've used both the aussie and the lock-right, they were nearly identical. Definitely go rear. There's a reason why trucks that only come with one locker have it in the rear diff. Stronger diff, weight transfers to the rear when you're climbing and/or accelerating, not going to foul up your steering, etc.
Coming from someone who has actually done it several different ways (auto locker, e-lockers, ARBs), I can honestly say there is nothing wrong with a good ol' auto locker. For the price, nothing can touch 'em and the tradeoffs aren't bad, especially in an ass-heavy rig like the 80.
Best bang/$ mod for any unlocked off-road vehicle. The difference in traction is night and day. Go for it!