you can purchase a brand new diff like a kazz, nismo, cusco, tomie....all come in 1 way,1.5way, 2 way. kazz diffs start from $1100 delivered and are well known and and are really great.
you have about 3months ?(could be more or less? or so to trnasfer to vic plates.....all you need is a rwc and thats all from my knowledge. can always ring vicroads to be 100% sure