"According to the link, "As of January 1, 1958, no cast iron wheels could be applied to new or rebuilt cars."
That information is correct as are the majority of the dates listed within the document. One exception is the date listed for the prohibition of all cast iron single plate, non-bracketed wheels. That January 1, 1952 date was extended to January 1, 1953. It should be noted that single plate, non-bracketed wheels cast prior to 1938 were prohibited in interchange at this time. This, as with most of the following, would not be noticeable as applied to our models, yet still historically valid.
As is aptly mentioned within the document the larger capacity of freight cars was the major factor in the demise of cast iron wheels. 850 pound wheel weights were rated for 70 ton capacity cars and commonly applied to covered hoppers. In 1954, The AAR's arbitration committee upon the recommendation of the wheel committee added a new Paragraph (4) to Rule 3, Section (w); Wheels, cast-iron, 70-ton capacity, prohibited on covered hopper cars, built new or rebuilt on and after August 1, 1954, and on all such cars in interchange on and after January 1, 1956.
The latter part of the rule was subsequently extended to January 1, 1957 and (again) to January 1, 1958 which was final. Paragraph (5) was added at the same time; Wheels, cast-iron, all sizes, prohibited on all cars built new or rebuilt on and after January 1, 1958.
"A new design for chilled wheels was adopted in 1950."
The new specifications took effect on March 1, 1950. Prior to adoption the AAR allowed several thousand wheels to be built to the specifications which were marked AARX.
I commend the NYC writers for their nice overview and especially note their proper use of "bracket" as opposed to "rib". Rib is yet another term which I have never seen used within wheel specifications, nor discussion thereof from The Master Car Builders Association, The American Railway Association or the Association of American Railroads. I would (as always) enjoy comments from the guys that actually worked for the railroad if "rib" was used within their description(s) of such wheels.