simply there is no basis for challenge , it is not the letters v8 themselves that is a unique mark, but each of the logo's show use's unique art work that is protection under trademark law
I think they did consider it that way - Henry's advertising definitely used the V8 as if it were the model designation in the pre-war period. Here are some examples ... 1934 Ford brochure: "Features of the new Ford V8 - New beauty of line, Beautiful interiors ..." 1934 Ford Truck brochure: "The log of the coast to coast Ford V8 Truck" 1935 Ford brochure: "All New Ford V8's are distinguished by their finish and appointments both inside and out" 1940 Style book of the 1940 Ford Cars: "The Ford V-8" and "The De Luxe Ford V-8" It didn't seem to happen so much after WW2, but I did find this example ... 1950 Ford brochure: "The Ford V8 for 1950, Deluxe and Custom Deluxe" I guess it petered out when the choice of models started expanding and it made more sense to focus on that instead, e.g. Sportsman, Crestline, etc.