First, as a reply to Ionized, I don't think you can tunnel ftp because ftp uses that back-channel on port 20 for the data? If you succeeded, I'd be interested in how you did it.
I'm not quite sure what you want to accomplish, "ssh over ftp" doesn't mean much to me. I presume you want to be able to ssh in *from the outside* to your box? In the Linky setup, go to "Advanced", "Forwarding", and set port 22 to go to the IP of your "ftp box". Along the same lines, if you want to allow incoming ftp connections to connect to your box, enable port 21 to go to that IP.
That implies that your "ftp box" does not get a DHCP address from the Linksys but has a fixed IP on your LAN.
ftp (if it's not anonymous) is such an unsecure thing with the cleartext passwords. If you just (as I do once in a while) need to get at files on your home box while at work or elsewhere, consider using scp across the fully encrypted (including passwords) connection, and not enabling ftp at all.