My information on this topic is fairly limited. A request to the McCormick-International Harvester Archives might be able to provide more information.
As far as I know, IH bought tires from all three of the majors, using them interchangeably. Here is some limited information about the regular ag tread rear tractor tires that these companies were making around 1950. Advertising for each of these tires can be found in publications from 1950.
Firestone: "Champion Ground Grip"
This was a closed center tread, with curved bars. The outer end of each bar was at decidedly less than 45 degrees. At the center, it was more than 45 degrees.
BF Goodrich: "Hi-Cleat Silvertown"
This was an open center tread with straight bars. Bars were at about 45 degrees and alternated long and short bars.
Goodyear: "Super-Sure-Grip"
This was an open center tread with straight bars. Bars were at about 45 degrees and all the same length. This was typical of what you think of for the "old 45-degree treads."
Not long after this, BF Goodrich came out with the "Super Hi-Cleat" that they claimed "sells for 20% less than first-line tire." This is the open center tread with "arrowhead cleats." Each tread bar was in the general shape of a checkmark. BF Goodrich replaced the Hi-Cleat Silvertown with the "Power-Grip" with a tread essentially the same as the Goodyear tire. Evidently Firestone went to a similar tread while keeping their "Champion Ground Grip" name.
IH sales brochures from the early '50s include pictures that feature all 3 of the 1950 styles as well as the BF Goodrich Super Hi-Cleat style. Some other tires, such as cane, rice or industrial types, were available on specific tractor models or for use in special applications.