Has an AFL game ever ended 56-7?
Exactly once. On June 8, 1901, Sydney beat St Kilda 56-7, and no AFL game before or since has ended that way. When it happened it was a scorigami, the first 56-7 in league history.
That makes 56-7 the 3836th most common final score out of 6,607 that have ever occurred in AFL. One point away, 57-7 has happened never and 56-8 has happened never.