It was pretty ordinary. It's a '51 Plymouth, a low-priced model in its day, and without any collector value when GF was filmed. What's noteworthy is that Carlo kicked out the real windshield, which was made of safety glass--laminated so it wouldn't shatter and send sharp shards of glass into anyone. That tells me the production crew bought it at a junkyard, and probably junked it after that scene was filmed, because replacing the windshield would have cost more than the car was worth at that time. By comparison: in an early scene in Goodfellas, young Henry Hill breaks windows of cars in a parking lot,pours gasoline into them, and torches them. Those windows "shatter"--the production crew removed the real windows and replaced them with "movie glass," which isn't real glass and thus gives a shattering look. They would have replaced the real windows after that scene (they weren't really torched).