I've had some issues with my '80 K20 since I've been starting to put it back together. I really suck at wiring and figuring out the issues but, I purchased a GM Service Manual off of Ebay. It's been a great tool and resource for me during my whole project. I think they are 10x the manual that Chilton's manuals are. He's a link check them out.
http://www.ebay.com/itm/1979-Chevrol...2403c0&vxp=mtr