I am building a mutt pan from all of my mismatched parts. Total rebuild on 55FL Motor with a 49 front head and 51 rear Sifton 412 cam Linkert 74B. 57 trans completely rebuilt. Glide front end is also redone with new Forks by frank tubes and new slider bushings by Bills Cycle. I am now ready to attempt to derake the 51 frame. I ran this frame from early 80s to 93 with a 63FLH that had 66 shovel heads.The frame was raked about 1'2 inch when I bought it.All tabs are intact except sidecar loops.Bike handled well and was lots of fun. I now want to return the frame to stock rake.I have read and been told that the stock Panhead rake is 30 degrees. But my stupid question is, "30 degrees from the frame down tubes or 30 degrees from a perpendicular line running even with the bottom of the frame?" Is it possible to get a frame blueprint? Thanks for any advice and help.