I recently stumbled upon a declassified copy of the 1963 Pacific Command history on the internet. It contains more than 300 pages in a PDF file, which is way more than I'm interested in, but it did have a few references to COMUSTDC, such as the fact that there were about 4000 military personnel assigned there in 1963.
There is also information on what was going on throughout the Pacific that year, which may interest some of you. I flipped through several pages but haven't yet read the document in detail.
One of the charts included is this organizational chart of the command. It shows the Commander of US Taiwan Defense Command (shown as "COM TAIWAN DEFCOM") as Vice Admiral C. L. Melson.
The complete document can be found here.