Yamato-class ships at Guadalcanal

What if Yamato and Musashi replaced Hiei and Kirishima at Guadalcanal?

They make hits far more damaging, but the key variables are early Japanese radar and whether the United States can support a heavier response.

Replacing Hiei and Kirishima with Yamato and Musashi greatly increases the damage caused by any Japanese hit. Japanese night-fighting skill still matters, but the historical American manoeuvre exploited very close range and the difficulty of firing around friendly ships. Yamato-class radar was not historically ready for this 1942 battle, so fitting a usable set early is a more important change than hull size alone. Radar warning could turn the American attempt to pass between Japanese ships from a successful ambush into a disaster. The United States would also react to reports of Japan's heaviest ships, potentially bringing Standard-type battleships forward despite the oiler and basing burden. Improvised tanker conversions might be required, underlining that replacing two ships changes the logistics and opposing force as well as the gunfight.