Quaife, Kaaz, or Cusco. Depends on how much a dedicated racer you are. I would go Quaife only because it's no maintanance, proven, and on the cheaper side other than a TRD
or MR2 being sold used or by someone who bought it and is selling it new. A clutch type definitely if you are serious about racing around a track. Any LSD will improve upon you're car greatly even TRD
(which isn't bad).