Simple answer-don't! I recently purchased a set of 'Wheels & Bits Monster ' air horns from Amazon. I had bought these items before, which were easily fitted to a BMW Mini Cooper and a Chrysler PT Cruiser (what!). My local garage who I have used for over 20 years found it virtually impossible to install them without major 'surgery' to the front of the car. He estimated that it would take at least 1 days labour to do the job which for a pair of £12.00 airhorns was a no brainer. I will continue to stick with the originals.