Great choices. For no good reason, I haven't seen the last two. The Searchers is a landmark, not just artistically but as a cultural marker about how attitudes toward race / ethnicity were beginning to change. (16 states still had laws against miscegenation in 1967).

The western that had the biggest effect on me was the elegiac "Ride the High Country." I don't remember how old I was when I saw it, but it felt like the closing act for the classic American western. (There have been occasional westerns since then, of course, but largely with a kind of anti-heroic tinge.)