Seems like you have an IHC that was rebuilt/overhauled at Springfield Armory in 1964. May have a birch stock that was common in that rebuild period. It may also pre date CMPand have been a DCM sales rifle. I would keep the rifle as is, as it would be very costly to restore.
Nice arsenal rebuilds are becoming collectables in there own right and are a nice piece of history. Looking forward to some pictures.