Another question is can you class North to Alaska and How The West Was Won as westerns.
According to IMDb (not the final authority, of course, but a reasonable source), North to Alaska is listed as Comedy/Western under genre, and How the West Was Won was listed as Adventure/Drama/Romance/Western.
But Robbie's recollection of at least one scene in each movie where Duke is on a horse now takes them out of the category of "horseless" although they are MOSTLY horseless!
Chester