The link above has 14 pages of discussions.
Some errors were noted and discussed.
Don't take any wiring diagram, GM or otherwise, as 100% accurate.
Understand what you are doing and use the diagram as a guide.
The best "jpg format" diagram for visual clarity is on page 13.http://67-72chevytrucks.com/vboard/showthread.php?t=185856&page=13
Use this link and save image as you wish.
Jpg or jpeg is a compressed format.
If I save the above image and then attach to this posting, it compresses again and clarity is lost.
If you have a PDF reader, you can use it to see the pdf file attached.