The tiny bits of OpenBSD that are completely specific to the Sun3 port are basically the same as their NetBSD counterparts but with some additions. The major changes are:
Snapshots of the kernel and diskless bootstrap loader are available. If you want to use OpenBSD/sun3 get an Amiga (or any other m68k OpenBSD) snapshot and the Sun3 GENERIC kernel and diskless bootstrap loader then if you don't know how to set up a diskless box read the diskless(8) manpage. Once your have booted the Sun3 diskless you should be able to "cd /usr/src; make obj; make build" to get a native OpenBSD/Sun3. Before doing this kernel instrumentation ("ps", "netstat", etc.) will not work.
If you suceeded or fail bug me for help, kudos, or brickbats.
www@openbsd.org