ive got an 07 duramax/allison LS. a friend of mine has a 04, it has a cord for the block heater. i cannot find any such thing on my 07. i figured surely if his had it mine would too. although he said he did have to dig for it and it was tiewrapped from the factory by the passenger side fenderwell. does anyone know if this just comes on certain packages (optional)? or should my truck have it and where to find...many thanks.