The Chevy restoration package is free from Chevy and has more information and specs on these trucks than anyone could possibly need. They copy it and send via snail mail. I think I got mine in 2 weeks after talking to them. You will need the Vin Number to get the right pack.
Good luck
Rich
Chevrolet Customer Assistance Center
Chevrolet Motor Division
General Motors Corporation
P O Box 7047
Troy, Michigan 48007-7047
Phone: 1-800-222-1020