I'm betting that the regulator sold by Jim carter is made by Regitar. They are stamped as made in USA but what does that mean these days? It is not a digital/electronic VR but an actual old style unit with springs and points. Is it made to the original Delco Remy standards? Nothing these days is made to any standard that one would have expected 75, 50 or even 40 years ago.
Buy it, install it and if it works, Great! Don't ever discard original parts, however, because you will probably end up needing to rebuild them sometime in the future.
I have a Regitar in my Cadillac and AD truck. So far, so good. Neither came from Jim Carter.