I was told by the VA admin when I was trying to do the same for a headstone that was incorrect that any stone ordered and put up prior to 1980, all the application and info has been sent on to the National Archives, now where there I don't know. I would contact the VA Memorial services section and see if they could give you who to contact at NARA. I have not got around to my search yet or I could tell you. If its anything like dealing with VA its a series of circle conversations but if you stay at it eventually they will find someone who can tell you.