well I have no idea about VIC rules, but it's easy to figure out. Go to the website. You will find this general list;
]vic roads online services link
then click on the seat link;
vic roads seat link
and you will see it says;
Replacement Seats
Seats supplied as an option by the vehicle manufacturer may be fitted. An Engineers report is not required for this type of seat replacement provided;
* the seat is one supplied by the vehicle manufacturer as an option for that vehicle and is actually replacing an existing seat.
* the original seat mountings are used, and
* appropriate seat belts are fitted.
In cases where the replacement seat is not one offered as an option by the vehicle manufacturer and the vehicle was manufactured on or after 1 January 1969 an Engineer's report showing continued compliance with the applicable ADRs will be required.
For vehicles manufactured before 1969 the seat anchorages must be of at least equivalent strength to the original anchorages. An engineer should be consulted if there is any doubt regarding the strength of the anchorage or any part of the seat installation.