Having spent some time mucking about with 3rd generation Bitsamissing Magnas lately, I have been pondering the legalities of fitting a passenger airbag to a car only built with a drivers side one.
TE-TJ Magna came with either no airbags, a drivers side, or dual passenger drivers. It appears the SRS ECU is the same regardless of one or two airbags, and if there is a drivers side unit the wiring is all there already to plug in the other one.
Seems that all thats needed is the airbag dash cover (ie with the cutout in it), the airbag itself and the welding on of a couple of brackets onto the dash support beam.
I'm not sure the VIN would even tell you if the car had a passenger bag fitted, as it was an option on most models it wasn't standard on.
I'm guessing the "official" line would be similar to the silliness that Jo went through for his tyres, but surely there is some common sense answer here (yes, i know... Its Vicroads and common sense does not as a rule apply).