Mr. Moungovan,
I'm glad to hear you are enjoying it. I think, if you look closely, you can also see the 126 in the San Salvador roundhouse (to the left of 127's stall). Around 8:05 to 8:11 there is a quick shot that shows the 38. Apparently this engine was equipped with poppet valves. Do you know if this is true?
I have to say my favorite scenes were the line of helpers in what appears to be El Rancho and the mixed train running southbound to Guatemala City or maybe the shots of 57 y 127 like you said. Aww heck... I love it all...
Take care and be safe,
John