[eoc_Jason]

In the functions_search.php file, locate the fetch_similar_threads() function.

You can bypass the stock search code and pass it to sphinx. You can have sphinx return relevancy scores so it should work.

I do not know how often similar threads are updated. Are they created only when the inital thread is, or checked with every reply? If you have a really large forum your similar threads might get stale rather quickly (assuming they are only searched on thread creation).

I'm working on a big re-write of the sphinx / vB search. Basically making it act more like google (or any real search engine for that matter).... I'll be sure to add in a clause for the similar threads though just to be complete.

When it's done I'll probably post the code here.