My 1994 Ford Ranger has been successfully converted into a truck camper. The process took a while. Initially, I considered looking for a cabover/popup camper that would fit in the bed of the truck, but it turns out there’s not many that are affordable (used), take into account my truck’s 1500 pound payload capacity (sadly not very much), and are for small trucks.
I decided on putting a canopy on the truck. After a lot of time scouring Craigslist, finding one canopy that turned out to not be what I wanted, selling that one (made all my money back and it looked great on the truck of the person who bought it), and finding another canopy in California, I ended up with a nice older Leer canopy. It came with a rack on top (bike and boat possibilities) and I replaced the locks, cleaned it, and resealed the windows.
Inside is a shelf that extends from the front nearest the cab to about halfway across the back of the bed (idea borrowed from Steph Davis). This allows for more headroom and prevents a coffin-like space for sleeping, like a full length platform would make. I also can access my stuff without having to open the tailgate.
Last night I tested it out with some local camping and this weekend I’ll be staying at another campsite just out of town to test out my setup a little more. So far so good!