Has a FIBA World Cup game ever ended 81-70?
Exactly once. On August 19, 2006, Germany beat Japan 81-70, and no FIBA World Cup game before or since has ended that way. When it happened it was a scorigami, the first 81-70 in league history.
That makes 81-70 the 475th most common final score out of 1,178 that have ever occurred in FIBA World Cup. One point away, 82-70 has happened 4 times and 81-71 has happened 2 times.