http://www.rta.nsw.gov.au/registration/vsi06.pdf
Thats a link to the rta, they dont really say to much about seats, though i have been told that you have to engineer the mounts if they are to be replaced with aftermarket, i would call the rta to make sure.
Oh and alot of the time the RTA tech line guys are not sure what can be done or not so you may even want to talk to an aproved engineer, there is a list of them on the RTA site.
http://www.rta.nsw.gov.au/
Hope this helps,
Ash.