Perhaps one of our historians with 1970s NZIGP programs could help. The 72 GP was held on 8/1/72 a Saturday and the 75 GP was held on 12/1/75 a Sunday. I have a date of 9/1/73 for the 73 GP but that was a Tuesday so cant be right and I cant find a date for the 1974 GP which was held at Wigram because of the Commonwealth Games.
Graeme