Has a FIBA World Cup game ever ended 54-50?
Exactly once. On October 29, 1950, Ecuador beat Spain 54-50, and no FIBA World Cup game before or since has ended that way. When it happened it was a scorigami, the first 54-50 in league history.
That makes 54-50 the 240th most common final score out of 863 that have ever occurred in FIBA World Cup. One point away, 55-50 has happened never and 54-51 has happened 1 times.