I discovered that with System 7.1 I need to make sure to do a fresh custom Install with ALL the network options selected (including printers, etc.)  For some reason if I did a basic install, even though it looked like it has the right extensions, my network cards never worked.  I had to do the custom install.  It's weird.

After that, seemed like I could throw any NuBUS ethernet card at it and they'd work without any special drivers or software.