I am looking for parts for crestopane windows. Their windows were made in 1981. The parts I am for is the is the inside track. Which contains a string attached to the top of the track at the end of the spring is a clip that connects to the window. Iam looking for the track or the other parts. The window's are double hung windows and the number on the windows are the following, 20603111, 19801219, and 18301112, thank you.