[GMCPaul]

The first thing to learn is the assembly manual is broken down by year, at front it starts with 1967 and illustrates everything for the 1967, then it goes to 1968 and illustrates all changes made in 1968, then 1969 illustrating all changes made and so on and so forth until you reach the rear pages that depict 1972. So if you know it a item that never changed such as the truck cab its-self you know the information is in section for 1967, if your looking for 71-72 bumper mounting you go to the 1971 section as that's the first year it was changed and thus isn't shown under the 1972 section since no change was made. Initially it can be a pain to use but the more it is used the quicker you know what sections to look in for the information desired.
Our pet peeve about them is we just wish they had reproduced the entire manual without editing out the part #'s or sizes on fasteners etc.....
Paul Jr @ GMCPauls