There actually was an assembly manual in a great big book (several books, actually). The pages were in three ring binders, with tabs for each UPC section (1A2J, or 2B, or 5, or 11 or whatever; UPCs went from 0 - 14), probably five or six separate notebooks to house all of the sheets. We received a new complete manual at the beginning of each model year and then scattered updates throughout the year. As updates were received they were placed in the appropriate section and the old information was thrown away. At the end of the model year the whole package was thrown away and a new series of books started.
Although in modern times the sheets are placed on the job location back then the books were kept in the Production or Inspection office (not line side). If there was a question, say a part release question, or a wire routing, then a representative from the foreman's group (either the forman or the "Quality Man", his RH man) would make the trek to the office area to ask the question or do the research. The books were not available to the average Joe assembler.
Originally the same set of information was sent to all C/K assembly plants (as many as seven plants at one point). There were a couple complete sets of books per assembly plant: one set in the body shop, one set in the trim area, one set for final line.
Probably goes without saying but I wish now that I had kept a set, instead of just throwing them away.
K