For his size, Fury is athletic and quick. However, Fury is not athletic and quick. He is awkward and a bit ponderous. His opponents, like most heavyweights, are usually one dimensional and do not have the toolbox of skills to solve the riddle that is Tyson Fury. That would not be the case for prime Ali. Ali would have and would use whatever was necessary to beat Fury. Please don't get this twisted. I am not bad-mouthing the Gypsy King. It would be a rugged, difficult fight. Fury is a unique talent with the best heavyweight brain and chin since Ali. I just believe he is a bit too slow and uncoordinated to win more rounds than Ali would win.
Obviously Ali is quicker but a lot of that would be negated by the height and reach disparity. The fact that Fury IS quick for his size AND has that size would give Ali a lot of trouble.
Would he be able to handle all the physicality? Everybody thats clinched by Fury gets worn down quickly.
Dealing with Fury's clinching when Ali gets in range would be a difficult challenge. I think Ali would have to use his foot speed and get in and out quickly. I also think Ali would use clinching to his advantage, hitting Fury and going in for the clinch.