I am quite sure the HKS wastegate have stiffer or heavier spring for higher boost. I dont sell HKS product or is their agent so if you are interested, please check with the HKS agent / dealer in Australia. Though I must admit, I love to use HKS turbo if the pricing is right. I am sure the price I am selling is fair and cheaper than what a lot of people are paying for down here. Take note, I am not a dealer just a private seller. hehee
As for a part number, the garrett part no. is on the turbo itself. You should be more worry if I sell a turbo without a part number. It might be some 'made in china' GT28RS that most dudes are selling on ebay. At least mine is a HKS turbo maded by Garrett. hehe