Hi Gary;
Here's some info that I have on this "airframe".
This was the wooden mock-up of the P-35 "Drake Bullet" originally built by MGM for the studio process shots for the film "Test Pilot" in 1938.
It also appeared in "Too Hot To Handle" also from MGM in 1938.
Later it was used in "Flight Command", 1940, "Pilot No. 5", 1940, and much later in MGM's 1959 film, "Never so Few", where it was destroyed by fire while portraying a Japanese aircraft, on Lot #5 at Culver City.
Here's a bad image of the mock-up on the set of "Pilot No. 5";
As far as other Japanese aircraft in the film or at least said to be used are The Air Museum's (POF) A6M Zero, and a Ki-84 Frank. There is a photo of both of those aircraft along with the P-35 mock-up in one of my books, but I'll have to track it down.
I've got no idea on the UC-78 ID, but at that time there were a lot more of those aircraft around to use in films. James farmer's wonderful book, "Celluloid Wings", states that the UC-78 was still on the MGM lot in December of 1969 just before the famed "MGM Air Force" was sold off or scrapped.
Hope that helps!
Jerry