I I just installed CM7.1 on my SGS.  To my surprise, the google apps that I installed did not include the version of google talk with video chat.  The ROM I used to have was based on Samsung's stock Android (2.3.5), and did have this version of google talk.

Is it safe to install google talk from a backup created in my previous version onto CM7.1?

Barring that, how can I get this version on my phone?