All you need to worry about is exceeding the load capacity of your two rear tires. If the weight of the truck at the rear axle is 3,000 lbs. and your two rear tires support up to 7,480 lbs. then the maximum payload is the difference or 4,480 lbs. though that leave no extra capacity for pot holes, etc.
With 4400 lbs. at the outside and subtracting 1000 lbs. for gear and 400 lbs. for a safety margin, that means a dry camper weight of 3,000 lbs. would be "ideal". All you give up is having a dry bath in your camper. Plenty of campers for long bed trucks that weigh less than 3,000 lbs. including the Lance 950, 950s, 1050, and 1050s camper models.