So, I am watching Gunsmoke two part episode "Snow Train", and it features this baby face prairie, oil burning, walschaerts, with piston valves. Quite a few action scenes in snow. The train consists of a wooden baggage and coach.

Is it McCloud 25 ?

The episode features a terrific crash caused by what appears to be some Christmas trees on the tracks.

Steve, If memory serves me correctly, that episode was filmed on the Black Hills Central. Unusual, because it wasn't filmed on the Sierra.

If I recall correctly, the indian extras stood around and thought it funny that the film producers were running around trying to hurry everyone. They filmed it in the early spring so it would not be too cold and an unexpected warm front moved in and started melting the snow.
Doug vV