Original 1979-80 GMC & Chevrolet Truck Dealer Parts Catalog. This Parts Book covers the Medium Duty Steel Tilt Models W6N and W7N. This is what the Dealer used to order Factory Replacement Parts to Repair your Truck. It has Part Numbers, Group Numbers, Description, Quantity, Application and no Illustrations. It is in very good condition with minor wear and soiling [see photos].  Very rare and informative piece that will be a valuable tool for the GMC or Chevy Truck Owner or Collector.