Stevenson still loses.
Taft vs. Kefauver is the only outcome I can see where Democrats still win that year.
Taft vs. Eisenhower (D) may have been the best chance in history for an all-state sweep.
And nope, don't think Taft beats Stevenson nor do I think Kefauver would have been a stronger candidate than Stevenson. Taft's brand of old school isolationism would not sit well with most of the public outside parts of the Midwest/West in the post-WW2/Cold War environment. And being as he was the "Taft" in the "Taft-Hartley Act," he would not win that Northern industrial support of New Deal coalition crossover voters like Eisenhower did.
Also Taft was at least as much of an "egghead" as Stevenson, quite frankly the man was something of a dweeb, so he doesn't even have the personality/charisma factor going for him.