Firstly (and you've probably covered this already), there are very few applications where ssh isn't better than rsh - do they have a very good reason for enabling it?
Secondly, there are two flavours of rsh, one using Kerberos authentication (part of the krb5-workstation RPM package) and the plain old version (the rsh RPM). Which one do you need?
Enabling the plain old version should be as simple as enabling it in /etc/xinetd.d/rsh and pkill -HUP inetd (alternatively chkconfig rsh on may do the work for you).
Annihilannic.