Yes and No. Yes it is a GM Service manual and no in that Greg's description is too generic. This manual will not have overhaul data. In fact it may refer you to the Overhaul manual for some specifics. Another thing is Chevrolet and GMC are nearly the same and if you don't have a factory V6 you are pretty much good to go. If you can a GMC manual would be my first choice. Here are two links for reference and information purposes. Faxon is known to me and I have used them on numerous occasions. Wandering the stacks there has cost me a lot of time and money!
http://www.ebay.com/itm/1972-GMC-Tru...5ae526&vxp=mtr
or
http://www.ebay.com/itm/1972-ORIGINA...91e014&vxp=mtr