If you mean classified — yes, there are many. Notably there are documents about how to make weapons of mass destruction (notably the atomic bomb) that are still classified. Usually this is stuff that is classified under the special category of "restricted data" and exempt from automatic declassification review, though there are probably non-nuclear things as well in the realm of weapons.

If you mean literally classified "confidential" — I suspect not, only because "confidential" is a very low level of classification, and anything once classified only that has probably been declassified. It is possible that, over the years, there might have been something classified originally as "Top Secret" which has been downgraded to "confidential" over time — but that would still be probably unusual for this time period. Stuff from this time period is likely to either still be considered pretty secret, like weapons designs, or not secret at all, like old military plans. One would not expect there to be a lot of middle-ground over time.