Taipeimarc sent me this 1945 map of the area around what later became the Headquarters Support Activity (HSA) East and West Compounds. Though I can't figure out the exact boundaries of either compound, there is some interesting stuff here.
The East Compound was mostly rice paddies in 1945 but the map shows a building at the approximate spot where USTDC was located. Below that map is a page from the 1977 phone directory that shows the shape of the TDC building (#19 near the top of the map). Allowing for the fact that I don't think the phone directory drawings are exactly right, it might be possible that the original structure was built by the Japanese. If that's the case, there would have been a number of modifications to the building after 1945.
I've also added an aerial photo that was taken somewhere around 1960 below that shows the shape of the building at that time. I think it's fairly close to the way it was when I arrived in 1973.
If the structure shown on the first map isn't the original USTDC building, then it must have been torn down by the Americans because I don't see any other structures near that location that would fit.
What do y'all think?