If you have yet to purchase a Ford Mustang GT Coupe and a Ford Mustang GT Convertible, do so. Take them to the U.S. Muscle Car Tuner shop and, when asked whether you want them tuned as a Ford or a Saleen, press Down and select "Saleen". The new car(s) will have a very visible sign that says "Saleen" at the top of the windshield. They will also be upgraded to C/D class cars.