Pretty much identical in most ways! Depends on what parts you need. The most important difference is that the 519 was designed to deliver specified amounts of gasoline with the use of positive stop buttons that protruded from the side of the pump like Keith said! Cylinder and markers were identical, as was the top and sheet metal. Seems to me that the bases were different? I know there was a base that was shorter than the other one but not sure how it fit into the picture. No ID tag on your pump? Just look for the button stops on the side. Also, a copy of Jacks book would be your biggest help, as it has pictures of the 2 models! Its like the bible for pump collectors!
Good luck---KEVIN