Erik,
Here's the address for the website, just in case you didn't know what it was.
[www.colong.com]
Look for drawing D-059, in the freight car section. These were the 37'4" flats that were cut down 1909 D&RG AC&F SG boxcars in the 62000 to 63499 series.
I also have the D&RGW folio drawing for this flat car.