The 99RS didn't come with a LSD in the rear diff so I was looking at swapping one in. Only thing is in the US a diff is about three times the price it is over here. So my question is would it be possible to use a WRX RA model's rear diff in a 99RS with a A/T? I know I could use a 2K RS's rear diff but why do that when there is one here for about $100. So will it work? Do I need to check the gearing first with the dealership here?