Mavericks no longer lists all the available resolution choices for displays when you open the Displays system preference pane, but you can get to this list by clicking on the Scaled radio button.
OS X 10.9.3 introduced a new feature called pixel-doubling that can provide a sharper image on many third party displays. To access it, open the Displays system preference pane, and click on the Scaled radio button. The options that include “Looks like…” are pixel-doubled. Selecting the highest “Looks like…” resolution on a 4K monitor will come close to looking like true Retina mode, resulting in a noticeable sharper/clearer image.