__________________
M1s that were overhauled at major depots and arsenals in the 60s usually have marking on the right receiver leg, engraved with an electric pencil, which indicate the overhaul facility and date of overhaul. Your rifle could have also seen several unmarked overhauls. While your 6-52 barrel could have been installed in the 60s it is more likely that it was probably installed during an earlier overhaul. As far as the operating rod, 7790722 is an early 1960s replacement rod. Alot of these rods could also have the NM (National Match) marking. They were also used for replacements in service rifles as many more than necessary for N.M. rifles seem to have been manufactured.
It is just a guess as to when the op rod was installed. It may have even been installed by CMP.