Erik,
Yes, I think that it is pretty well accepted that the 484 and the 488 swapped tenders some time in the 1940's. It is easy to trace with the squared-off tender notch. The last date I recall seeing 484 with this tender was in some John Maxwell photos in 1941, as I recall. There was probably other K-36 tender swapping as well, but they are hard to trace except for this tender with the squared-off notch. On K-37's, it is easier to follow these swaps due to the unique patches, different heights of the coal bunker sides, etc.