My LGS might have a used mag laying around.
My '63 has a 35 rem marked mag.
Got a newer.243 mag as a spare, works fine (contrary to what was stated on a couple forums).
LOL
I had much better luck with my 35 760 using a 30-06 style mag than I did the 35 or short action ones. I'm not sure why but it worked better. A lot better.