What do you want to hear? The 6.2 is a great engine as-is. Get the 4.something rear axle if you are concerned about torque. As long as your little Lance is all you want to haul... Of course twice the torque makes a difference. Only you can decide how much that means to you. It will rev higher. The 6.2 likes that.
This camping season, my real world fuel consumption with a Northstar Arrow in the back was better than 19L/100km or 12.5 mpg. That was going around 55 on the highway (trucks over 3500kg/~7800lbs are limited to 80kph/50mph here). I hear it uses more when you go faster.
