I know nothing about Epiphones of any era, including those built in South Korea in the '80s, so take this fwiw.
I wouldn't conclude "set neck" meant "dovetail." Before the Age of Machines, dovetail joints required handwork reserved for any brand's mid/upper range. I think your PR 350S is in the lower range (
https://www.scribd.com/doc/133163274...talog-2003-pdf and search "was PR-350S" at that page). The link and search take you down the page to the DR-200S, successor to the PR-350S. No mention is made of the neck type, but if you look just a little bit above, at the DR-350, you'll see it's "the ultimate in acoustic tone", which suggests that's an upper-end model - that's the only model to say it's got a dovetail joint, suggesting the others have "something else."
The lower range asian guitars got all manner of neck joints, including necks held onto the top by connecting wood dowels (doweled butt joint, usually epoxied and sometimes bolted to hold during epoxy dry time). With this joint, the neck is held on by the glued fretboard and the heel that's epoxied to the top of the guitar, positioned by wooden dowels and held in place by a single bolt for gluing. It could also have a mortise and tenon (less common) joint that could be Martinesque (horizontal) or vertical at the front, under the fretboard. I'm guess doweled butt joint, as I know the '70s Epiphone FT 565, for example, used a doweled butt joint with a bolt. If you assume you have one kind of joint and work on it, you could wreck it, so baby steps. Look inside the soundhole at the base of the neck block - see a nutted bolt or capped bolt? Think epoxied doweled butt joint. Then search neck resets with this neck joint and you'll see most do a "bolt on" conversion to reset the neck because getting the epoxy apart is too big a deal. There's a guy on here named Jeff who lives in California who does bolt-on conversions for just this kind of problem.
Here's an example of an Epi doweled butt joint:
After your research confirming the type of joint, consider the Big Bag of Hot Water method of loosening inaccessible epoxy while you apply gentle pressure to separate the parts (after removing the nut and bolt stud):
http://www.acousticguitarforum.com/f...et+my+expoxied
Good luck