Is it possible to use Google to find Drupal with a specific version of Drupal?
Using Google Search it might be a little difficult for you. This search phrase can give you a few websites.

For better results you need some website profiler like BuiltWith to give you the list. The closest I came across was http://trends.builtwith.com/websitelist/Drupal-7 You have a list of Drupal 7 websites here but not 7.31 in particular. They might give you the details in pro-version but I have never tried.