OS 3.9: Sharing Dialup Internet to Airport and Ethernet

Can I share a dialup modem connection to BOTH Airport and Ethernet at same time. I have selected both in Sharing preference and sharing is ON. The Aiport shares the modem connection fine. The Ethernet does not. There are no option (in OS 3.9) to set the address range to share on the Ethernet port or to specify DHCP, Manual etc. Is it always 10.0.1.x and DHCP? Also I assume it is sharing using DHCP as there is no way to specify.The hardware here is an old ibook clamshell with builtin modem, airport and ethernet running OS 3.9.