This is one of those few occasions, size would not matter.
Wladimir is 6'6, Ali is 6'3, three inches is not much.
As for Klit's muscle, I think that would be a complete disadvantage. Ill explain why.
First Klit is not going to win the jab game against Ali, He has gotten very comfortable fighting guys much smaller and not having to move that much. There is a reason for that, his conditioning is horrible. He has gassed himself out in fights tragically when he is put in a position he has to punch.
Ali by comparison at his prime could move much faster and smoother...he would keep the fight at a pace Wlad would NOT be comfortable with. Wlad would know he is losing rounds in the outside jabbing game and be forced to follow a dancing Ali around the ring trying to make up points or get rounds. Under those hot lights and at Ali's pace Wlad would be gassed out by rounds 5-6.
And right as Wlad started sucking wind, Ali would start turning that devastating right hand over, catching him in the mouth. Now lets be honest, Corey Sanders (RIP) a full time bartender part time boxer, slammed Wladimir all over the ring.
Wladimir would be defenseless against Ali by round seven and would get brutally dropped.