The best tie downs connect to the frame.
You need a place in the truck bed for an electrical connection to the truck.
Start with enough truck and then you will not have to modify anything or overwhelm the suspension, bearings or handling.
A camper is a small space, even for one person if you are in it for more than a couple of weeks. If it were me, I would buy a small trailer for around the same money and tow it. Easier to drive because you are not top heavy. Easy to pull. YOu can leave it at your camp site. Much more room and comfort in even a 20 foot trailer.