Earlier on in the thread there was a suggestion of a US Army Centurion (or at least US markings for Korea) and I was wondering it could actually have happened.
My understanding was the M-24s struggled against the T34/85, the late model M-4 was a pretty good match, while the M-26 overmatched them but were compromised by their mobility in the terrain found in Korea, hence the types withdrawal and replacement with M-4s and M-46s at the earliest opportunity. At the same time the Centurion developed a very solid reputation for its protection, mobility as well as the accuracy of it's gun, with (apparently) many US infantry units preferring / requesting Centurions in the DFS role when available.
How about once the issues with the M-26 became apparent Britain was in a position to offer a regiment or brigade worth of Cents to the US for use in Korea. Possibly these could have been the five regiments worth of Centurions (also ten regiments worth of Comets were planned for the CMF as well) Australia determined they needed for their post war army but never ordered. In this alt they could have ordered them but made them available to the US for Korean operations.
Assuming this deployment went well the US could have even developed their own version with US engine and 90mm gun which could become the NATO / MAP standard tank before eventually ending up with a 105mm diesel powered version.