Converting ipfw.conf to iptables?

[Scott R. Ehrlich]

I recently received an ipfw.conf file from a friend's BSD box I was asked 
to translate to Linux's iptables.   From what I've seen thus far, CentOS 
has /etc/sysconfig/system-config-securitylevel that doesn't seem that 
expansive.

I haven't fully ventured into the Ubuntu firewall config, yet.

What is the best, easiest way to perform the conversion for both CentOS 
(5, 5.2) and Ubuntu (8.04, 8.10).

Thanks.

Scott