Thanks again agracier.
There were 50-70 airbases on Formosa, most of them were small strips apparently, but the Tainan complex was large. The place names have mostly changed though so finding them can be tricky, I'm still trying to track down where many of these places actually were. The larger and/or notable bases were: Einansho, Hsinchu, Karenko, Koryu, Koshun, Matsuyama, Shinchiku, Tainan, Takao (Kaohsiung), Toko (Seaplane Station), Toshein, and Toyohara Airfields.
Other targets on Formosa were Kagi, Shoka, and Chosu, towns with large railyards; Takao, Yulin Kan Bay, Kaohsiung and Keelung were important ports. The 5 railway bridges linking Keelung to Kaohsiung were considered important targets. And the Hsinchu oilfields in the northern part of the island.
Keelung was probably the most important port:
Our own shipping-intelligence data, analyzed at Washington, indicated that Keelung had an average of forty-eight ships in port per week at that time, traveling under great hazard in order to keep supplies moving southward to Japan's front lines, and foodstuffs moving northward to Japan proper. American photo reconnaissance in 1944 showed a crowded harbor.
The codename of the proposed invasion of Formosa was Operation Causeway, and it was hotly debated in Washington when to invade the place, they didn't invade it after all but Nimitz considered it to be more important of an invasion target than the Philippines even and it wasn't until November '44 that they decided to not invade Formosa at all. In fact, some Navy planners wanted to skip Okinawa too and go straight for Kyushu, which would have been...interesting in a Chinese curse sort of way without taking care of either Okinawa or Formosa first, in my opinion.
There's a lot of info on Formosa scattered around, the problem is getting the place names lined up since some are old Chinese, some are Japanese and some are new Taiwanese. Adding to the trouble is Allied reports tend to mix the Japanese and Chinese names into the same report, sometimes in the same paragraph willy-nilly.
Still trying to get a "Population Volunteer" from among my guys, but everyone seems to either be busy, or terrified of learning new tricks.