factory special dodge dart

I am in the process of trying to find information on a 66-68? dodge dart that came from the factory with some rare special features. This is what I know about the car; the car came from the factory in orange paint, had a 383? or bigger, and the suspension was set up for the car to go in circles (race)? This is all I know about the car. I don't have the VIN # and the second owner recently passed away. Any knowledge is greatly appreciated.