Safe bet would be a Dana 60 or 14-bolt Bad bet would be on a Dana 35
You're somewhere in the middle - if it ain't broke, run it for now and save the $$ for another axle. Just don't expect it to live long, and I wouldn't put much, if any, money into upgrading it....
Run it until it breaks, go to the junkyard & get some spare shafts for backup. When it breaks get a D44 & call it a day. I ran 35's on 30/44 for years with no breakage of the 30 and everyone said it was impossible. Welded, hub conversion, etc. etc. It held up fine. Some people have a lighter foot & can 'feel' when they're exceeding the break point.
Oh I forgot to mention I wheel with a guy who has a cherokee and runs 35s on a 35 and he has never broken an axle shaft and he is harder on it then I am.