It was all quite thoroughly reviewed in 1992, and any documents not released had to have good enough reason to be kept classified to convince the National Archives committee.good argument- except that any sources are dead by now, and methods from 60 years ago aren't likely to still be a secret now.
Two subsequent administrations (Trump and Biden) have elected to keep some of the documents classified.
That's some freakin' conspiracy when all these people who couldn't possibly have anything to hide are choosing to keep the docs classified.
Unless maybe Biden was on the Grassy Knoll that day