Many thanks to the person that responded to my query about LC3 cards!!
(Sorry, I have the message on another system.)

I have added the lctest.tgz kernel to a test system and I seem to be
getting results I can live with. If you need an LC3 tester, I would be
glad to be a victim. (I have several to choose from, but I do not
currently consider myself a kernel expert.) I'm about to begin doing
some real work with these systems and would like to move from pppd to
ethernet.

If anyone is interested, here is what I have found on my test system
(more details as needed) :

Configuration: NetBSD V1.4.1 with lctest.tgz kernel (pretty vanilla)

With DynaPort E/LC (DP8392BVF)
  System hangs on any ifconfig command

With Macintosh LC Ethernet Adapter (DP83934CVUL-20)
  It works!!! many many thanks!!! Please note the following messages:
  "sn0: Tx packet status = 0xc"
  "sn0: receive FIFO overrun"
  The messages tend to be generated when there is a lot of disc
activity.

Also note that the new kernel does hang from time to time (may not be
related).

brian