If you truly want the most durable beast you can find, I'd have to say the '08-'13 2500 trucks. The 6.0 motor is going to easily be the most durable, and no AFM! And probably the easiest to service, since everything under the body has been around since about 2000.
I've beaten the ever-living snot out of my '08 2500 for almost 5 years. Bought it in 2013 with 100k on the clock. It's now up to 175k, and is still PERFECT. Not counting maintenance and tires, I've spent a sum total of $23 in repairs on it - bad purge valve solenoid I replaced myself. I've logged well over 20k miles pulling trailers well over 7,000 lbs all over the country. I drive it like I stole it, and haven't even had to replace the brake pads yet.
It's a 3LT trim level, so it has all the options - quad heated seats, bose, nav, backup camera/sensors, power tumbling middle row seats, sunroof, rear DVD video. Oh, and it'll pull an 8600-lb trailer into the Rockies, too. While carrying 7 passengers. Think of Conan the Barbarian wearing a tux.
Some of our greatest hits...
Running the "Ike Gauntlet" up 11,000 feet in elevation with a 7,000-lb trailer...
My son did this...