Hi Clark,

According to the ATSF reefer book, USRA rebuild classes Rr-19 through Rr-27 (the Long's and Intermountain models) were all built in 1936 through early 1940 with wooden running boards and hatch platforms with the hatch hinges toward the end of the car.  Beginning with class Rr-28 (1940), the rebuilds received abbreviated wooden hatch platforms, and steel running boards and platforms were introduced after WWII.

Ted Culotta's "Essential Freight Cars 33", published in the August 2006 RMC, is a great article that shows several classes from the Long's and Intermountain models with the appropriate details.  He included a Sunshine kit of the Rr-34 through Rr-43 classes, all of which look pretty much the same and had the steel running boards and platforms.  I think one could build a nearly correct model of these cars from the Intermountain kit using some different parts (ends, fan control boxes, etc.).

The classes and built dates (from the ATSF reefer book):

Rr-19    31254-31655   1936-1937
Rr-23    31656-33155   1937-1938
Rr-25    33156-33655   1939
Rr-27    34500-34950   1939-1940
Rr-27      4200-4248     1940            (cars w/ fans)
Rr-28    35000-35499   1940
Rr-32    35500-35999   1940-1941
Rr-33    36301-36650   1941
Rr-33      4251-4400     1941           (cars w/ fans)
Rr-34    14280-15399   1941-1942
Rr-34      4401-4750     1941           (cars w/ fans)
Rr-35      7029-7358     1944-1945  (cars w/ fans, US Gypsum running boards, 7" eaves)  

Todd Sullivan