480,
The 64 was never changed into the San Juan style. The San Juan RPO's (54, 60, 65, 66, 119, 122)used to look more like the 64 with end Platforms. The Window configurations were similar to the 64, but each were different to each car. During the 1937 San Juan Modernization, the D&RGW picked the 54, 60, 65, 66, 119 and 122 to be rebuilt. The lost the platform and had their window configurations somewhat standardized, the Ends of the cars got the Rail Renforcement and other changes.
As mentioned before the 64 was not rebuilt and instead assigned to the Salida Wreck Train along with ex-coach 0460 and two converted cars into work (Block and Tie Car) flats. So depending on what era you like the 64 is closest to how all the RPO's were originally produced.
Kevin Cook