Wait... you live in Spearwood Western Australia, right? You do know that there is NO restriction on owning replica firearms in WA, don't you? Owning Gunformers is perfectly legal and unrestricted in WA! (reference)

Although be aware that Customs is a Federal body, not state, so if your toys are seized by Customs you will need to obtain a Form B1709A Importation of Firearms - Police Confirmation and Certification Permit from the Firearms Division of the Western Australian Police to have them released to you from Customs.