I keep intending to look into XModem file software for OSX for file transfers to Apple][s and early Macs. I hope there's a good thread or two on this forum to help.
It's easy to miss in a thread that seems to wander around a bit, but did
you see this post? Napbar has successfully used ZTerm & XModem protocols to send Mac binary files directly from OS X to a classic Mac running MacTerminal. This is based on
the method I have been using with a Keysapn serial adapter to transfer data from a MacBook/Tiger running Sheepshaver and Clarisworks/MacTerminal 1.1 to a 128K Mac using MacTerminal 1.1. Of course this method is a bit slower than AppleTalk, but considering the average file size on a 128K through SE, that's not a huge problem.