Here's a good summary from a few years ago when this popped up. In the case of a Prado, the 120 is fine as they're designed to be removable, the 150 that has the seats in the floor could be classed as a modification.
Transport South Australia’s view is that removing rear seats, where no tools or only simple tools are needed; where no structural modifications are involved; no change in vehicle category and no commercial gain is sought; does not need approval and so is not committing an offence. Providing no anchorages for seat, seat belt or child restraint are removed or modified, no modification has been made to the seating capacity. However, if the seat cannot be returned to its original position because of the removal of an anchorage point, then a permanent change in seating capacity has occurred. To formalise this change in seating capacity, an inspection will be required and following inspection a certificate of exemption issued for the permanent removal of the seat. Where the seats are removed to change a vehicle registration category; to skirt established arrangements such as ADR certification; or to make a substantial structural change relevant authority approval is needed. If any change in classification is sought, an inspection is required and a label attached accordingly.
Vic Roads’ view is that there is no reason seats that are designed to be removable cannot be removed. Doing this does not alter the seating capacity of the vehicle. Seating capacity is defined by the Australian Design Rules as the maximum number of seating positions for which the vehicle is designed; not the number of seats actually fitted at any point in time.
The NSW RTA’s position is similar to Victoria’s in that rear seats may be temporarily removed without affecting the vehicle’s compliance.
Queensland Transport says that for vehicles fitted with quick-release seating attachments as original equipment, temporary removal of the seats is acceptable. In the case of vehicles fitted with bolt-in seats no engineering approval is necessary for temporary removal, provided the category of the vehicle does not change as a result of the seating reduction. At the time of a Safety Certificate inspection, the vehicle must be returned to the manufacturer's original condition or have a Modification Plate fitted for the seating configuration as presented. Queensland Transport will mutually recognise interstate drivers travelling in Queensland who comply with their own jurisdiction's requirements, but drivers are advised to carry some proof of this compliance.
