I'm looking in to purchasing a spare tire kit and I've been looking around the web for the best deals. I've noticed that sites will advertise spare kits for the 15" wheels and the 17" wheels. However, when you look at the part numbers...they're the same. Is there really a difference? Has anyone ordered a set for the 17", and if so, can you verify the part numbers for me. Also, where did you purchase it from if you don't mind. Thanks.