First of all, is this plausible? Everything I've seen seems to indicate that it was the Democrats that wanted him in 1948, I can't find any mention of a Republican attempt to draft him. But had he been a little more open to the idea of running then, perhaps the GOP would have pursued him more strongly.
Assuming he does run, can he win the nomination, and go on to beat Truman? How would an Ike presidency four years earlier look, especially in regards to the early stages of the Korean War? And concerning domestic politics, I'm guessing he does not pick then Congressman Nixon as VP, which likely means a far different career for him as well.