Direct answer
If the vehicle is registered in Victoria, read Transport Victoria’s guide to vehicle modifications. That page lists modifications treated as approved for the purposes of the Victorian regulation it cites, points at Vehicle Standards Information sheets, and explains when VASS certification is required. VSB 14 remains the national technical code underneath.
Why this page is useful — and dangerous to copy
Victoria’s approved list is specific: additional compliant lighting, certain air filters, single-tone air horns, alarms without remote start, bull bars that meet the cited VSI, cargo barriers to the cited standard, plumbed catch cans, gas shock absorbers that keep original attitude, HVAC that does not ruin demist performance, and more. It is also conditional. The same page says the approval does not apply if the work is carried out so that the vehicle no longer complies with a standard for registration.
Copying that list onto a national blog as “Australia’s legal mods” is how bad advice spreads. If you are not on Victorian plates, use it only as an illustration of how a jurisdiction writes, then open your own agency.
Exhaust and lighting in Victoria
The Victorian guide publishes an exhaust block that applies instead of one VSB 14 modification code for that jurisdiction, including the requirement to retain catalysts, sensors and particulate filters in their original locations. Lighting additions are approved only when they comply with the standards for registration. Window tint is approved only when it complies with the tint VSI. Those sentences are Victoria’s. Read the live page for amendments.
VASS
Significant modifications in Victoria are commonly certified by Vehicle Assessment Signatory Scheme signatories. Find current signatories through the channels Transport Victoria publishes. This site will not name commercial engineers.
Next
State rules hub. Check with Transport Victoria or a VASS signatory before you modify the vehicle.