Why not just upgrade to 3.8? It looks and works virtually the same.
I agree, actually 3.8 is the same as 3.6 but with bugs fixed and a with some more compatibility fixes (e.g. PHP5) applied + some new freatures. Am I right?
3.8 has new features like visitor messaging, social groups, thread prefixes, human verification manager (I think) is better in 3.8- and tabs in user profiles instead of static pages.
But most of the above can be turned off or ignored and keep a nearly identical look for 3.6.