One drastic step I've tried is to make a filesystem under 386/netbsd,
   put the right files there and copy the image to the RZ32L on the
   DECstation (5000/120 now that I think to mention it).  It complained about
   not finding ultrixboot, so I loaded the kernel via mop.  I didn't get
   the "WARNING: no swap space found" message, but got a message about not
   finding a disklabel.

Labels are at a different location on the i386.  You could manually
copy the data from sector 1, offset 0 to sector 0, offset 64 and it
would probably work.

(I had to do similar hackery when the label location changed in the
hp300 port due to 4.4-Lite.)