New (to me) Lance 815 truck camper owner. Got a few q's

After you add propane, water, clothing, tools, cooking gear, food and miscellaneous the rig with weigh another 1000 pounds more.

To handle the weight, you should consider Rancho shocks and supersprings or equivalent. Tires are a major concern. You need to be sure you have tires that will handle the final weight and you need to be sure they are always at the correct pressure.