I wasn't questioning your statement, it was the OP's idea that it may be an Acacia Ridge Sandman without XX7 as it was imported to NZ.
I did miss the 1979 bit but overall it doesn't matter really - in 1979 a 253 HQ Sandman van or a 253 4spd HQ van would be worth about the same, the Sandman probably cheaper in those days as it'd be dearer to insure for many. It would be like a 5yo SS ute today vs an SS Thunder ute - swings and roundabouts in value.