The factory image and binaries for the Nexus 5 are now available as Google promised. You’ll see that the Android 4.4 build is KRT16M and the codename for the Nexus 5 is “hammerhead,” just like we told you months ago. Assuming you own a Nexus 5 (which you don’t yet), you’ll probably want to keep these files around in case you plan to tinker. A factory image can restore your device to its stock state should you run into any issues.
The binaries are available as well.
Android 4.4 Links: Factory Image | Binaries
Update: Hangouts .apk with SMS can be found here or in the comments.