http://www.transport.qld.gov.au/reso..._vehicles2.pdf

This PDF from Qld Transport lists modifications in 4 categories:
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Minor:
Many minor modifications can be carried
out with the approval granted by this
booklet. Details of these modifications are

outlined in Section 1.

Complex:
Complex modifications such as engine,
gearbox and rear axle, steering and brake
replacements require approval from an
Approved Person. Details of these
modifications and the Approved Person

Scheme are outlined in Section 2.

Specific:
Some owners require approval for
modifications which may be outside the
scope of the Approved Person Scheme.
Details of how to obtain approval for these

modifications are outlined in Section 3.

Motorbike:
(Similar content to cars.)
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Cheers, Ross.