Same axle and frame as your 04. 2 less rear tires and lighter springs.
If you're intending on going by the rated capacity on the door placard then skip it and get a dually. If you're only concerned with what the truck is capable of, then the axle is good for 10klbs. OE wheels are very conservatively rated at 3500-3600lbs ea and you can get tires up close to 4000lb rating.
Means a total cargo weight of about 4000lbs on the rear axle, with the right suspension for "stability" is good.
If it's a long bed, a shorter camper will likely transfer some to the front axle too.
Gvwr will be the most conservative if you're set on going by the mfgs numbers and you'll get hung up at around 2500lbs even though the truck isn't yet breaking a sweat.
