You should be able to find a mustang in JFK. You can get the LDW for $9 a day if you stayed with the compact car, or depending on how they charge your upgrade you could pay up to, $26.99 a day.
Though i do believe that JFK has a partial damage waiver just for the tires and windshield, which is a fraction of the cost, i just don't know the pricing on that.
Enjoy your travels.