The numbers came from Chevrolet Truck Chassis Service Manual for C-K trucks 1967-1971
it's out of print but if you search American Classic truck parts they sometimes have used copies in good condition. They also have a an online VIN decoder and one of your numbers is a partial VIN... which agrees with my manual.
http://www.americanclassic.com
These guys saved my backside when I started my 67 stepside...same problem you have. Some gomer pulled it out of a field in Texas and proceeded to cobble together a truck out of whatever bits he could find. To fix it I had to ID all of that stuff he did. The only thing that matched was cab and Frame.