Please excuse this late response in regards to the comment about the GCR's 4960. You are entirely correct...she bears little physical or mechanical resemblance to the machine that the Burlington purchased in 1923.
But consider this, if the Santa Fe had purchased her back in the 40's they would very likely have made some of those changes themsleves, especially changing out that small capacity tender...it just would not work out with 64 miles to go between Williams & the Grand Canyon.
I have no problem at all with whatever GCR decides to do with any of their motive power, steam or diesel. They do not pass themselves off as a museum operation & thus are not bound to keep equipment in an "as built" condition.
If you want to witness one of the great steam shows still remaining for any of us to see, get yourself out to Anita some day ahead of the train & listen to either 29 or 4960 race by @ 40 per, all the while preparing for the 6 miles of 3% just ahead. There's nothing out West quite like it.