Hi Nathan
I have looked on Carjam and have confirmed the numbers:
7A889030700055688 is a number that NZ authorities call the VIN (it is not a VIN issued by GMH)
CD388985 is the engine number for a 2850cc (173ci) (This is not a GTR engine. GTR engines have the prefix JL and are 3300cc (202ci)
8B69DCZ756970C appears to be the VIN issued by GMH. The first part 8B69DC makes sense but the rest of it does not.
The 8B69DC means 8 (Holden) B (Luxury level S Model) 69 (4 door) D (Engine type 2580cc 173ci) C (made between Sept 1972 and Aug 1973)
It the GMH VIN tag was from a GTR, the prefix of the VIN would be 8D11L meaning Holden GTR 2 door JL engine.
No Toranas were built in NZ but there were many imported.
If the car that you are interested in is a 2 door - then it appears that it has been fitted with a 4 door GMH VIN tag and an incorrect engine.
The car may be a GTR or an S Model 2 door.
Until you have access to pictures, it cannot be ascertained whether it is a GTR or S Model
Cheers
Bazza