Two years ago I had a 1986 Wellcraft Starwind as my first sailboat. Sold it and bought something bigger but while I had the Starwind, I went through EVERYTHING on her.
The keel is about 6 feet long and about a foot or so wide and houses the center board. The board, as has been mentioned, doesn't have a great deal of weight to it but the keel itself is almost all lead. Try rapping it with your knuckles! When I had mine, I also found formed lead ingots placed in the bilge around the centerboard trunk - I was never sure that these came with the boat or if they were added leter by a PO to increase the ballast.
No matter how much ballast you have or add, the 19 is a "tippy" boat and is sensitive to wind and waves. I always had the feeling that in anything over 20knots wind speed, she could go right over. It was actually a lot of fun to stand her up on her side, playing the main sheet and tiller! BFS all the way!
If everything else is in good shape, I wouldn't worry too much about the ballast weight. Put a couple of people in her and have them shift as needed.