FC 179, I did not think it would have been a problem to just have a different gearbox fitted as long as the steering, suspension and engine is standard or, if the gearbox installation standards of workmanship were deemed to be poor when it was inspected or defected.
Has the car been defected?
Did you just buy the car and you are now wanting to register it?
Do you have a roadworthy list from the vehicle inspector already and are having trouble interpreting what they require?
I would suggest if it is the first two, you should just get a permit if it is roadworthy to drive or hire a car trailer and book it into the roadworthy inspection team, who will do an inspection and give you a list of things to alter/change for your vehicle to be able to comply with their protocols.
Alternatively (which is what i would recommend to anybody in SA) you could email vehicle standards officers on:
DTEI.VehicleStandards@sa.gov.auoutlining your vehicles modifications and then they will send you a form which you fill out, detailing your mods and they send you an email back, letting you know what is required for the inspection
http://www.sa.gov.au/subject/Transport,+travel+and+motoring/Motoring/Vehicles+and+registration/Vehicle+inspections/Roadworthy+inspections