While NARA does not hold the records of corporate entities such as General Motors, GM does have quite an extensive corporate archives which might be of use to you in your research.
GM Heritage Center
If these documents were generated by GM about their vehicles, they may be able to assist you in discovering more information about these missing era records.
I hope this is helpful in your research!
That was one of the first places I contacted. They don't have any records before 74 I believe. Do you guys have newspapers and magazines from 63 and 64?
Thank you for contacting History Hub, Cody,
The National Archives is the nation's record keeper, and preserves and makes accessible the documents and materials created in the course of business conducted by the United States Federal government. Therefore, the National Archives does not hold newspapers or magazines unless created by the federal government.
Chronicling America is free online database developed and maintained by the Library of Congress that provides free access to information about historic newspapers and select digitized newspaper pages.
You may also wish to reach out to the Newspaper and Current Periodicals Reading Room at the Library of Congress, whose staff may be able to direct you to other useful resources. Contact information and a link to Ask-a-Librarian may be found on their website.
There are numerous online collections of newspapers, however no single collection is going to be comprehensive and many require paid subscriptions. One free site is https://news.google.com/newspapers however the exact date spans of newspapers they include vary greatly.
Was there a specific newspaper, geographic area, or topic you wanted to research?
One of the first things to do in order to find old newspapers is to contact your local public library. Many libraries have collections of their own or have institutional subscriptions to online databases. If you know which newspapers you are interested and those newspapers still exist, you should also contact the newspaper company directly so they can let you know what options exist for researching their previous issues.
All the best of luck on your research!