I believe the Malibu lowers are a bit different size as well but will "work". I think they are smaller and don't fill the area completely.
The Malibu will also have the molded in arm rest (plastic) where the Pontiac G's have the padded, removable arm rest.
The Malibu will also have the molded in arm rest (plastic) where the Pontiac G's have the padded, removable arm rest.