There are 3 types of BNR34 N1 turbos. AA401, AA402 and AA403. All specificiatios are same, but AA403 is better for others because NISSAN and Garrett modified it.
Early model of R34GTT has the trouble with sensors and inside of ECU. It is easy to cover in Japan. But I do not know in Australia. But I am not sure your trouble is by that or nor.
R34GTR standard Turbo is C100/GT25, Compresor is A/R0.53, Turbine A/R is 0.48. R34GTR N1 Turbo is C106/GT25, Compresor A/R is 0.60, Turbine A/R is 0.64.
R32GTR Oxy sensor is not much concerned for the feedback to ECU. If you can make ECU as well, you do need Oxy sensors. R33 and 34GTR are difficult though...