Found an error in a wiring diagram

So I am helping a good friend with a frame off restoration on his 67 Mustang. Yeah, I know, it's a Ford. I said he was a good friend, not that he has good taste in cars. Anyway, we are 95% done with it now. I was running the wire harness for the factory AC (following a wiring diagram), and I noticed that something didn't seem quite right. After a few minutes of thinking "this cant be right", I looked in another book. He has two different books with wiring diagrams in them. Guess what, the other book showed the harness to be hooked up like I thought made sense. I guess my point is that even if you own and follow a wiring diagram, you could still have problems. FWIW, I have been working on car wiring for a LONG time now, and this is the first time I've seen an error. Tomorrow I am going to contact the company making the book with the error. Anyone want to guess what their response will be?