Yes. I don't remember what model year but it varied by final assembly location. My '87 is laminated, and I think my '80 was laminated.
Site member "chipflyer" does reproductions. I'm sure he can tell an original from a reproduction.
http://outintheshop.com/
You can contact the GM Heritage Center Archives, depending on your model year. For US built and/or sold light trucks after 1976 you can send them your VIN and $50 and they will return the actual vehicle invoice for your specific truck, which includes RPO content and pricing.
http://www.gmmediaarchive.com/?page=1
GM of Canada has information reaching a little farther back, for vehicles sold in Canada, or vehicles produced in Canada for US consumption.
http://www.vintagevehicleservices.com/options.html
If you don't fall in either of those categories you are out of luck.
For the original build: The SPID is a service document. The truck is contented and all of the build information broadcast throughout the assembly plant to the areas required. The build manifest, specific build sheet, tuneup labels, tire pressure labels, VIN tag and SPID document are all created to match the truck as a result of that process. The build sheet is what communicates to the assembly floor how the truck is to be built.
40 years after the fact: It's a mixed bag. The hardcore restorer will build the truck as originally equipped; some percentage of guys build the truck the way they want. A few will make a new SPID to match the added content; from what I've observed most do not go to that effort*. You probably won't be able to tell unless (a) you have the build sheet or something else documenting the original content or (b) you ask them.
*In reviewing this thread I see one person that made a new SPID to match their added content.
K