If I'm not mistaken, 3rd row was only available if ordered from the factory and could not be retrofitted. Unless your S had it from the factory, you cannot add on unless it did and was sold by the original owner. So if your S was not configured for 3 seats from the factory, you can't put one in and neither should you since the factory also added extra reinforcement in the rear bumper to keep the rear occupants that much safer.