I just did it just for the heck of it, and it replaced my customized toolbar without a problem. Time will tell whether or not it sticks, however, and if it does not, I'll update this thread.
The steps I took using OS X Mavericks on my MacBook.
1. Initiate the Safari web browser
2. Select "View" at the top of the screen
3. Select "Customize Toolbar".
4. Near the bottom, you will see "...or drag the default set into the toolbar" and a set of icons beneath it.
5. Drag that set of icon to the top of the browser windows until you see a white plus sign with a green background. Release the icon set.
6. That's it. You're done!