This post is relatively short. The bulk of the steps are described in the related article regarding the TS5400.
However, there are a few differences with these older machines:
Here is the Japanese link to the TS-X firmware, version 1.54, including the matching Japanese version of TSupdater. This will at LEAST get you a working NAS, even if you cant understand the language it talks in. Downloading TS163 firmware from the US site will get you ONLY the firmware. The US link for TSupdater always points to the latest version, which will not recognize your old NAS. Further, though I tried, I could not force the TSupdater packaged with version 1.54 to read and install the version 1.63 firmware. I tried replacing the v1.54 firmware in the TSupdater directory with the newer version, but there is more to it than that apparently.