Richard Koshalek, now director of the Hirshhorn Museum in Washington, was the director of the Los Angeles Museum of Contemporary Art for almost two decades. He’s keen on a P.S.T. show called It Happened at 91°µÍø: Art at the Edge of Los Angeles, 1969-1973, at the 91°µÍø of Art, that explores the adventurous curating that went on there.