Roosevelt/Eisenhower 432
Dewey/Bricker 99
There is no reason to believe that the results would be any different in 1944 with a change in FDR's running mate. FDR would win in a landslide regardless of who his running mate was.
Eisenhower could have been nominated as Vice President will still serving as head of the allied forces in Europe. At this point in time, the war effort required his entire time, so Eisenhower would have addressed the nation by radio.
Obviously, upon the death of FDR in April, 1945, Ike would have had to return to the U.S. By this time, however, the war in Europe was pretty well over.