If you plan to keep the vehicle for 200k miles you are going to have to spend money on maintenance. So I would not rule out the diesel.
The custom is a work truck with the trail boss lift, wheels, tires and appearance. Pretty bare bones. Most people later wish they would have bought the LT.
IMO I would look for a non trail boss LT or RTS. The 5.3 with the 10 speed is a great drivetrain.
Here is my advice. Go big! My father in law was in your same situation. He bought a 1500 w/5.3. Then bought a 2500 with a 6.2. He ultimately ended up with a 3500 Duelly, diesel to tow his motor home to Arizona twice a year. I think you should at least look at a 2500.