Joe Louis of the Rocky Marciano fight VS Tony Galento of the Louis fight. Who takes it? In my opinion, Galento breaks the old Louis down with a KO in the mid-rounds, perhaps similar to what Rocky did, but maybe even sooner as Galento was a quicker starter and more aggressive right off the bat. I don't see any way an ancient Louis remains standing by 15
Louis would still put up a fight, since he still had an excellent jab, but his inability to put his combinations together like in his prime most likely result in him eventually getting knocked out.