As mentioned in post 8:
http://www.fordgarage.com/pages/twobladedfans.htm
Paragraph 3 of Vince's webpage as mentioned above:
1. The Model A fan was very prone to cracking
2. was replaced with an improved construction Model B style.
3. The Model B fan was also known as the Holley design fan.
Paragraph 4:
Version 2. At a glance it looks like every other fan, but it is a much improved construction, and was Ford's fix to the fan cracking problem which was becoming apparent at that point in time. These improved Model B fan blades are made from a single piece steel stamping.
Comment: This second version of stamped steel fan
might be the one that is called "cast"?