Hi cordwainer.
Here: "Realistically, none of these agencies or companies has anything to lose by releasing archived records from a closed, 55-year-old, well-publicized public investigation. But I began my research from a point of cynicism as to whether some of the people you contacted for information really knew what they were talking about. Or if they pointed you in another direction just because they didn't want to be bothered. Both are a lot more likely than them trying to hide something or stonewall you."
I must disagree. No matter the length of time involved, any reopening of a "cold case" brings with it the possibility of civil and criminal litigation.
Why? Because in the US, there is no limit to prosecution or litigation IF it can be reasonably demonstrated that there was fraud in any official testimony related to the incident. Fraud can be demonstrated easier than one may think, since even an "innocent" representation that is false might be construed as fraud.
I most certainly am not trying to suggest there was any thing improper in this investigation.