Hi,
the replacement for that is named org.hibernate.search.engine.integration.impl.ExtendedSearchIntegrator, but if you need to use it could you please let me know why? It's not considered a public API, so if you are needing it we're probably missing to expose some functionality in a better way.

To get a reference to it, use the unwrap method:

getSearchFactory().unwrap( ExtendedSearchIntegrator.class );