As I remember, despite misinformation from years ago, the receivers are fine. Probably closest to thing to the actual M14. Its the bolts that were a problem. A bit on the soft side, which may eventually lead to excess headspace. And the barrel, while good, may not be compatable with a US GI bolt. When rebuilding I think most just use the receiver.
Since you have a headspace gauge, I would shoot it and enjoy. Check headspace and deal with it if it becomes an issue. Fulton Armory knows these rifles well if/when the time comes.
BTW, as I understand it, our brothers to the north in Canada can still buy these cheap.
http://www.marstar.ca/gf-norinco/M-14S.shtm