In order of cost and performance ( no coincidence ) :
ARB air locker
Toyota Elocker (have to do a few simple mods to make this one work)
Detroit locker
Aussie locker
Lockright locker
I wouldn't fool with a trutrac if it were me. In extreme low traction situations they don't perform much better than an open diff.
I ran a Lockright for a few years and didn't have any problems with it, but the Aussies have a better rep than they do. They just weren't available when I went to buy so I got what was.
If you can swing it, get an ARB or mod in a Toyota elocker from a newer model truck.