With a PoD no earlier than December 10, 1941, try to have at least one of the six carriers (Akagi, Kaga, Soryu, Hiryu, Shokaku and Zuikaku) to strike Pearl Harbor survive the war. Obviously, the carrier doesn't need to be in good condition - it can be rusting away at Yokohama - but it does need to make it through the war intact.
Bonus points if it doesn't get expended in postwar nuclear testing, but instead gets preserved as a museum.