Fully compliant safety chains and D shackles are available for caravans up to 3.5t ATM. 

Current rules state that the chain must be marked according to the Austrlaian Standard and be appropriately rated for the ATM weight of the caravan. D shackles do NOT have to be rated, although it is highly recommend that you do you appropraitely rated D shackles / bow shackles.

Different rules apply to vans from 3.5 to 4.5t ATM.