Some of the stuff (e.g., rarpd, bootpd, dhcpd etc., libsa) still will only support Ethernet. Tcpdump itself should be ok, but libpcap needs lot of work. For the detailed change history, look at the commit log entries for the is-newarp branch.
and "seconds since 1970" (POSIX time_t). See sys/arch/sun3/sun3/clock.c for an example of how these can be used.