It'll come down to a battle of personas and Willkie would have probably crushed Wallace. Willkie was a pretty popular guy and he was very John McCain like in how respected he was.
Wallace would get good grades for the war but when it comes to Russia, his social ideas and all the rest he will get downgrades. Defiantly see him pushing civil rights against everyone's desires and causing the southern dems to revolt. Who would they nominate? Have no clue. But I see it being a southern conservative to appeal for that vote. Maybe Harry Byrd Sr perhaps.
I'd say Willkie wins by a comfortable margin thanks to the split Democratic vote and most of the south goes Dixiecrat.
This is best case for the Dixiecrats.
Best case for Wallace if he goes hard liberal.
If Wallace goes more moderate he could pull off a close one.