I don't see why they wouldn't. The police package (9C1) engine and tranny are just built heavier. The engine is beefed up a little more and so is the tranny. As far as I know they'll fit right in there.
The 2011 Chevrolet Impala has a V6 engine.
The 2001 Chevrolet Impala has a V6 engine.
The 2005 Chevrolet Impala has a V6 engine.
The 2013 Chevrolet Impala has a V6 engine.
The 2008 Chevrolet Impala has a V6 engine.
The 2009 Chevrolet Impala has a V6 engine.
The 2004 Chevrolet Impala has a V6 engine.
The 2010 Chevrolet Impala has a V6 engine.
The 2007 Chevrolet Impala has a V6 engine.
The 2002 Chevrolet Impala has a V6 engine.
The 2006 Chevrolet Impala has a V6 engine.
The 2012 Chevrolet Impala has a V6 engine.