Like the others have said there are a lot of choices. I had the Lock Right, Auburn Gear Pro series limited slip, Detroit locker and the Eaton/Detroit Truetrac.
For offroading I like the detroit locker. But for something with excellent street manners, no noise, no special differential additives, and no clutch packs to wear out I'd go with the Truetrac. They recommend regular dyno gear oil though and not synthetic.
http://www.eaton.com/Eaton/ProductsServices/Vehicle/Differentials/detroit-truetrac/index.htm
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