I can't seem to find any confirmation, either way, on whether
the Ki-45 at Garber is a complete aircraft or just the fuselage
missing tail section and wings/engines.

This is the twin engined night fighter right?

As I recall from the book Restoring Museum Aircraft the whole aircraft was
restored sometime ago. The internal equipment is incomplete especially the air
intercept radar equipment. But there are photos of the major components being
restored.

John Dupre'