Foreman (Katello) Smart proxies from different versions

I have a new install of Katello on CentOS 7. That is working fine, the
local smart proxy works fine.

I have another puppet environment on another machine that is running
another katello instance with puppet. This server has all my puppet
environments and I would like to setup a smart proxy to get this
information to my newer Katello machine.
My question is how do you do this when the older version of Katello is only
compatible with el6. The newer instance of Katello wants to use
foreman-proxy-content but it is only available with el7.