I did some more reading on the internet today and found some notes here and there that said networking on the 68K Macintoshes could be accomplished between two Macintoshes by the simple expedient of connecting them with a printer cable and installing some software.
The recommendation I read was Network Software Installer 1.4.5 from Apple, unfortunately 1.4.5 requires a superdrive. I downloaded 1.4.4 which creates an 800K diskette. I transferred it to my MacSE. I opened and expanded the file creating an 800K diskette. I ran the installer on the SE and rebooted with no problems.
I set up my MacPlus and ran the installer, which ran fine. When I rebooted the MacPlus, I got an error about the coprocessor not being there. I had two 100MB ZIP Disks set up as hard drives for the MacPlus. I tried the installer on both and had the same results. The MacPlus would not boot with the 100MB ZIP drives. I removed the system folder from both and reinstalled OS 6.0.8 on them to get them to run again.
Upon further thought, I think I will move the file I downloaded from Apple to the MacPlus and then create the 800K diskette on that machine. The SE is upgraded to a Prodigy SE by SuperMac which has a 68020 and a 68881 coprocessor. I think that may be the problem.
The 68020 was definitely the odd man out. Only two Mac models came standard with it: The Macintosh II in 1987, and the Macintosh LC in 1990.
And that was it!