I think Tyson would beat Ali. Douglas, fighting the fight of his life against a less than best Tyson, had success with the jab, but mostly because of what he threw behind it. Tyson's whole game was based on drawing a jab, slipping it and countering with something hard, and he was very fast. Douglas maintained distance, made Tyson react to the jab, then countered with other punches. This made Tyson stand up and hesitate, and easier to hit with the jab. Ali's movement would play into Tyson's hands, let him get his forward motion rolling. He'd slip that jab and get to Ali.
And Ali would be at a disadvantage in that event because of his poor punching technique. He had a good right hand, but there was no shoulder in his jab, and he dropped both hands when he threw uppercuts. He never in his career learned how to block a left hook. At his peak, Tyson was faster than Frazier, and a two handed puncher and he'd stop Ali.
Ali's best chance to beat Tyson would be the Ali that fought Foreman. Frustrating Tyson and tying him up, potshotting him with right hands. Tyson didn't like to fight much inside and didn't know how to deal with a guy trying to wrap him up.