https://www.youtube.com/watch?v=ACWMbeXd31sa 30 min video hosted and narrated by the President of Fisher body in 1959.. addresses the operations performed by Fisher Body, and the process didn't seem to change greatly from the mid fifties thru the late sixties... and probably later..

This is a very interesting video..

the numbers themselves are mindboggling.. how much steel, material, glass, aluminum, etc is used to produce the almost 4 million car bodies per year (in 1959) across the five divisions. At that time, there were33 Fisher plants, 9 of them stamping plants...
Every 'old chevy guy' (and gal) should watch this..