Thanks for the welcome! The GM Heritage Centre is GM's archives
https://www.gmheritagecenter.com/ They will send you a printed build sheet for a fee and several days wait. The sad thing is I used to provide support to GM and had access to this information direct.
This only works if you have an American spec'd truck. They said my truck is built with Canada base equipment and forwarded my email to them. The Canadian team responded, call my local dealer or visit the heritage website. Yup, big help.