Squid "behind" a firewall

We've placed a Squid on our intranet (behind a firewall) and I've read the
FAQ regarding Squid behind firewalls, but our setup is somewhat different,
and I'm basically after what others have done in terms of security and such.

Now, Squid is only allowed to open ports tcp/80 and tcp/443 out through the
firewall.

Obviously this limits squid very much :-) So we're reversing the rules so
that Squid may open any port it wants, except ....

Which ports should a machine running Squid not be able to open? Is there a
list of 'recommended' ports/ranges somewhere?

--
Espen Lyngaas, IT Consultant, Color Group ASA
Espen.Lyngaas@colorline.no Espen.Lyngaas@c2i.net
http://www.team17.com/~elyngaas/
Phone: +47-95063143 +47-22944315 ICQ: 43241796