First off I'm sure there are a thousand threads on here with this subject but I have had a hard time locating any. My question is what are the upsides to each of these shift kits. I've had many a gas gm truck but this is my first dura. It's an 01 CC/Sb, bullydog power pup programmer aside from that stock drivetrain. The truck has 155k on it and tows regularly. What would you guys recommend? Thanks in advance.