Sorry to hear about Nagy's death. But if I wanted a large capacity magazine for a bolt action, I think I would start with a .308 Mauser and adapt it to FAL or M14 magazines. A better rifle, a lot less work, and available magazines.
i dont know the consensus is on these things, but a co-worker has one and it works well, the mag has a hangup every three or four loads, poss due to surplus, i really kinda want one, but i think mosins are so pretty in original furniture