Dean's Mustang
From Super-wiki
In the altered timeline of 6.17 My Heart Will Go On, Dean dives a 65 Ford Mustang. It has the Kansas license plates "KAZ 2Y5" which were seen on the Impala for all of season 1 and most of season 2, until 2.20 What Is and What Should Never Be.
A 65 Mustang was Kripke's original casting choice for the role of Dean's car.
When I was originally writing the show I wanted to give the guys an American muscle car. My first choice was a '65 Mustang. My neighbor said it has to be a '67 Impala, because you can put a body in the trunk. He says, 'You want a car that, when people stop next to it at the lights, they lock their doors.' Source.