I have never seen a Fisher Body manual that was dated before 1965. If you look at the Factory Service Manuals prior to 1965, you will see that they cover many of the body issues that would be addressed in the later Fisher Body Manuals. An example is my 1963 Corvair FSM supplement covers the folding top, which was introduced in mid 1962.
What I do find interesting, is that there are many years and brands within the GM line of cars, that a factory assembly manual isn't available for, but it is available for Chevrolet. Is it that no one has a copy to reproduce or there is not enough interest to reproduce?