I bought a 2007 trailblazer 4.2 v6 with a bad engine and bought a replacement engine from a local junkyard that will not take back it is from a 2003-2005 I know that it has been done with a 2007 engine into a 2003-2005. I also understand that this is a down grade but what will I need to change to make the 2003-2005 engine work in the 2007