You can try e-bay, some stuff is genuine and some is repro. I just ordered an original stock from a guy in Holland. He also sells original cleaning rods and hoods( hoods $23 and rods $40 shipped). Not cheap but guaranteed original. His e-mail is 5mei@planet.nl He has a website, just google k98k mauser stocks and 5mei should be on the page somewhere. He has a pretty good reputation on the military surplus forums.
I think 1940 were unmarked but someone may correct me.