Here's a partial scan of the C-25 erecting card (Crystal River 103) available from the Degolyer Library at SMU.
I was looking for similar C-21 details and, as also suggested by Dave, acquired from DPL's Rio Grande Papers collection a K-27 footplate drawing and C-16/C-19 footplate drawing - partially edited scan attached.
Figured the dates and sizes were roughly comparable, and Baldwin wouldn't make radical design changes between these particular engines (I would assume). Also, while obviously very different, the C-21s were very similar to the C-25, especially in details reflecting D&RGW standard mechanical practices. Does that make sense. There could be enough front end detail similarities between the two classes to make C-21 photos useful.
From the DPL online digital collection, a detail of 375's frontend from an Otto Perry photo, Durango 1938. There may be others that are helpful as well, especially with the zoom tool.
Hope these help.
Mike