If your are looking for a Hellanbach GT for LoveMedia crazy car give-away, there are two ways to get one. The first is to complete level 4 in the car salesman missions. It will appear in the showroom. The second place it can be found is at Shoreside Vale. Go to the first house on the bottom row of houses in the Cedar Grove area. Look in the driveway to the garage. If one is not there, drive left or right, then turn back. There should be one sitting in front of the garage.
You can also get the Hellenbach GT during the mission where you must kill the Sindacco gang member. JP will call and tell you to take his car as a down payment on the money that he owes you. That car is a Hellenbach GT. Save the car in your garage until you need it for the Love Fist car giveaway.