While the 1200 was sold in some markets as the Datsun 1200 GX, I do not believe that they were ever offered outside japan with the 5 speed.
The 5 speeds that are available in PNG are very likeley to be the conventional shift 60 series overdrive gearboxes from the 1400 Bakkies, & while these are VERY good, they don't offer the same sporty performance of the lovely [non overdrive] 56A five speed models.