Check out any Davis Craig supplier. They will be able to supply what you need. I know that these guys aren't strickly automotive but give Cummins Australia a call and check out what Fleetguard can offer. I have had great sucess with Davis Craig and Fleetguard units in the past on both motor, transmission and diff cooling. They work well even in areas of less than perfect air flow. I have had them incorperated with the dry sump / remote filtration fit outs I have done. Be Warned! Shop around for the best price they can be a bit on the expensive side but there are still bargains out there, stick with the bigger parts suppliers

Stevo with you being in Newcastle give Driveline Services Australia a go. I believe they use Davis Craig units with the Mark Williams diffs. I am sure that someone will be able to help if you have no luck there get them to contact their Brendale branch and source the infomation.