The CIA has declassified 28,000 documents of Presidential Briefings from the Nixon and Ford administrations. You can go here to search them.
The problem, though, is that they are heavily redacted. Here is one example for Chile from September 1972.
These documents are over 40 years old and very few of the protagonists are still alive. It is hard to imagine the rationale for blocking so much except for embarrassment of some kind.