Looks off in my opinion for that time period. Ali still had a very fluid signature in the mid 80's. His signature deteriorated over time but this one looks off to me even after it deteriorated. However, I would not consider myself an Ali expert but I am relatively familiar and since no one else gave an opinion I decided to give mine.
Thanks for the comments so far. This piece was cut from a book, and later sold by a collector to me. I've matched it to numerous PSA certified pieces from the same era, and nothing about the handwriting raises an alarm to me.
You're right sorry, for some reason I have 82 stuck in my head. Even so I don't think his writing got shaky till late 90's when his letters got smaller? Maybe someone can concur