Okay AlexisDetroit. Nothing difficult is ever easy, I guess. NTSB investigates all aircraft accidents in the U.S. that are not military on military/public property. Except they didn't exist until 1964. Before that the Civil Aeronautics Board did accident investigation. Except they were disestablished in 1985 or so. They sent their records to NTSB. Had a nice phonecon with the NTSB records people and they can not find anything in their holdings.
CAB records also went to the national archives and I think I have identified and found the right records class (CAB Office of General Counsel -accident investigations 1952-1969). Inquiry off to national archives and we'll see what happens.