Confirming genuine classics can be difficult and requires intimate knowledge of the make and model to be certain.
I would contact Holden's customer assistance people, give them the id numbers of your car and ask them to check against their production records.
If they can't do that contact a club such as an HSV Owners Club and ask them to help you. There isn't a club in the NT, so contact another state's club.
A guiding range for the value of your car is $38,000 to $46,000, but it can vary widely depending on originality, condition, kilometres done etc.