I'm going to look at a 2006 GMC 3500 4x4 Dually this weekend. I need to know what to look for. I'm confused about what motor is in it (LBZ,LLY,?). I'm new to the Duramax scene so any help would be nice. All I know about it as of now is it has 148K on it. Should I be worried about the trans ? If I do end up with it what are the mods ya'll recommend ( exhaust, intake, programmer,etc..) I will do it in stages as money permits. Thanks in advance.