My be it is better to go with a wrx sti diff. I think a 2004 and 2005. details are in a thread if you do a search. They are a direct bolt into place they are a 3.9 and a LSD wolf creek in the states make an adapter so our 1/2 shafts bolt up. The sti diff are visually identical other wise any diff rebuilder can rebuilt you diff easily but the cost is going to be about the same as getting a LSD diff
I have bought and fitted them. good quality leather and excellent workmanship. They also fitted perfectly. They are cheaper than I could buy the leather alone. Got to be happy