I think Qawi would brutalize an Ali of the second Spinks fight and stop him by the 10th round. Ali still had a great chin and fantastic ability to take punishment, but Qawi would set the pace and Ali would fade as Dwight got stronger round by round. Ali didnt have the power to hurt Dwight either, and God help Ali if he tried to pull a rope a dope which I think he would. After 10 one sided rounds Dundee refuses to let Ali take anymore while Bundini begs for one more round.
Even a 1978 Ali would still have enough left to beat a 1986 version of Qawi. Dwight would n't have the necessary power at the higher weight. Muhammad would take a scrappy,untidy decision. Lots of holding involved.
It would involved lots of holding from Ali, and would be close over the 15 round disatnce, ending in a disputed decision one way or the other.
Even at this advanced stage of Ali's career,he'd be too strong to be brutalised by a 1986 Qawi. If he does n't allow Dwight to outwork him,Muhammad wins a unanimous decision in a slow paced fight.
What was Ali's reach advantage? I know Frazier was short but he still dwarfed Qawi and Ali was still able to jab and tie someone up in 78, which is what he'd do all night long against Qawi. It may be a bit similar to M Spinks-Qawi actually except even more boring and with more clinching. Ali still has enough to take a UD though.