you need a slk32 or srt 6 diff. the gearing on the n/a version has different gear (3.27 vs 3.07)
call devil at unitrax and asked to be put on the group buy standby list. that way if they build more than the g/b you can get a unit or if someone drops out they go down the standby list.

lastly if you hear something break DONT KEEP DRIVING IT!! you are just doing more damage . remember if you buy a used diff it may not be any better than the unit you just lunched. could last yrs or days