Hi Bill:
Yes, 464 was the Chama plow engine for most of the 30s. 460 might have been used in the late 20s (it had the large wedge plow for a while), but I have found no D&RGW records for that period. The D&RGW used wedge gon 09271 out of Gunnison, 464 served the same purpose out of Chama. The reason the D&RGW used the gon out of Gunnison was there were several branches where the mudhens were not allowed (Baldwin, Pitkin, Lake City, Floresta) and the wedge gon could be used with any locomotive.
In the late 20s, a freight train was run on the Chili line separate from the passenger. K27s and 28s were both used on these freights. I think by 32 that K28s were doing all of these. When the 490s were built, they pushed the K27s off of most main line service.