You know, I just looked through the websites and only Hertz -I think-offers the Mustang from JFK-so perhaps I used Hertz because I originally wanted a Mustang for the same fun reasons as you.
But perhaps you fancy something a little more daring?
Orlando Exotic Car Rental: Rent a Luxury Car in Orlando, Florida
But of course, if it is your wife you are taking, then I guess the Mustang will siffice?