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Michael Spinks
vs.
Eddie Mustafa Muhammad
CANCELED

The fight between Michael Spinks and Eddie Mustafa Muhammad, which was to take place on July 15, 1983, was canceled after Eddie Mustafa Muhammad failed the weigh-in. Here's the beginning of an article from the New York Times about the cancellation:

TITLE BOUT IS CALLED OFF

N.Y. Times Article
July 16, 1983 New York Times.

It's unsure what HBO aired instead. My guess would be their fight from exactly two years prior, but I honestly have no idea.