The Alamosa/Antonito section had rail all the same height. What is in question was the main line through the Royal Gorge to Leadville. I have read several sources that the inner rail was smaller.
*Interestingly, the last narrow gauge train under steam between Salida & Leadville happened on February 19, 1911. It was a C&S train consisting of engines #59 & #65 and several cars that cleaned out the remaning engines and rolling stock that the C&S had stationed at Gunnison. With the Alpine Tunnel closed, This train was moved over the D&RG tracks over Marshall Pass to Salida.
Narrow Gauge cars continued to be moved over the D&RG tracks behind standard gauge freights using an idler car between Leadville & Pueblo into the '20s until the 3rd rail was taken up.
Regards,
Donald Foster
*Source: Colorado Rail Annual #12