['68OrangeSunshine]

"Factory Assembly Manual" is really a fiction aimed at the post-vintage aftermarket restoration crowd -- US --you guys and me.
Yes it is sort of an assembly manual, but really the book is a compilation of GM's notes to dealer service centers on Retail Purchase Options [RPO]installation. Probably they were faxed out from Detroit, back in the day. [Maybe mailed out to Mayberry.] The randomness is testimony to the fact that there was never any intent by the original document producer, the Manufacturer, for there to be any such compilation. Also original copies of RPO guidelines had OEM part numbers in 7 digit format. The empty spaces in the " Factory Assembly Manual" loom out like empty caption balloons in an Orphan Annie comic. At any rate there are no part numbers listed in the Red book now.
Maybe there were copyright issues? I'd bet some critical notes on installations were also didacted. Could be a lot of these dealer shop guys were trained in Michigan, and all spoke in a code that is lost to us non-employee enthusiasts. I wonder if you heat some of the pages with a candle, some of the lemon juice instructions come into view, however briefly. JK.
The Chevrolet Truck Chassis and Service Manual and the ... Overhaul manual are both genuine documents, and worth owning by the serious owner operator.