I am not sure if this is even available anymore. The first time I looked through this manual, I was at a public library. I found it helpful so I went to the local bookstore to purchase a copy, so I did not have to drive the 15 minutes back to look for some basic information. The manual I am referrring to is, Chilton's repair & tune-up guide for Mustang 1965 to 1973. Covers all models. The book has a part number 6542.
I have had this for years and used it quite a bit. I plan on keep using as I still have my 1970. The manual included the electrical diagrams (which I found and find very helpful), troubleshooting and even basic bodywork.
If you need some specific information, and I can help, let me know. I'll be glad to look through the manual and provide you with the information.
Best of luck. Rick
