Abu
My principle source is the Wylam Materplan. Not only does it have all the ribs, formers, etc. but has minute detailed measurments for every station and every fixture and feature on the plane. While i have no idea if they're correct it obvious that someone must have measured a real pfalz to be so meticulous.
For example would you like to know that the tire thread was 4 inche wide? or that the width from the center of the tire thread to the edge of the inner wheel bearing was 3 1/4 inches? The plans also show the differences between the D-III and the D-IIIa. I did the "a" model because it has a bigger horizontal stanilizer. From the front edge to the rear edge of the cockpit was 26 1/4 inches. Stuff like that.
I have a number of other sources of pictures and photos (Profile) etc. But the plans came from the Wylam set.
alan