Louie, NZ$360 is equal to US$255
Hi smuller81 - 5f 7c 3r will be fine. You will get a little more drive to the rear wheels that's all. If you can find some 1000 diff oil use this with the 3000 in a 50/50 mix in the diff to give you 2000 weight.
The centre diff normally has 2-3 shims on the spur gear side (rear) and 1 on the opposite end. It is possible that a couple of shims missing would cause the diff housing / bearing to jam against the tower. Try shimming it as above and see what happens.