I recommend Quaife or Wavetrac.
I've used the Wavetrac for over 10 track days now w/ no probs, so it's good enough for occasional track duty. Changed the differential oil twice already at 12K miles, and it still looked good. Didn't do a used oil analysis, but at the very least, no visible metal shavings seen, and wasn't too dark
No abnormal sounds or anything heard after 25K miles on it.