IT's a great question because Wladimir is, as close to the perfect boxer as one can be. He throws every punch correcly, blocks well and doesn't waste punches or, for his size, power.
The problem Wladimir runs into is that he has never faced a fleet footed adversary like Clay. Now, if you're talking about the 22 year old kid, who embarrassed Sonny Liston, he presents a serious problem for Wladimir. ALI-64 was NOT prime. He didn't reach his prime until 66-67. Still, because of the way Clay fought, Wladimir would have problems. It's the one style he would have trouble solving because Clay could move for 15 rounds, while Wladimir doesn't perform well, if his opponent is not right in front of him.
With near equal reach, the 3 inches height difference becomes meaningless. This is because there is a drastic difference in how quick the jab is used. Clay is much faster. Also, it doesn't matter what your power advantage is. It's rendered useless when you can't see what's coming at you, or catch this guy who keeps hitting you.
Wladimir would want to impose his strength. However, once he moves in, Clay darts away. In the rare occasion that Wladimir would catch him, Clay would clinch just long enough to dart away, even before the referee could break them.
Wladimir would land punches. The problem is that he can't put enough of them together, at any one time, to seriously hurt Clay. After missing so many punches, a fighter's arms become 50 lb. clubs. Wladimir is, perhaps, the best conditioned heavyweight of all time. However, he still has never had great stamina. Chasing, swinging and missing would sap any fighter's stamina.
Clay W 12.
If it's 15, Clay by TKO in 14.