The conversion truck camper kit has all the information you need with instructions to take a truck and build a camper either starting from scratch or with a camper shell.
I have seen a few people build one from the bed of a truck, now this is extremely difficult, but it can be done.
You will more than likely need help from friends and family as you start from scratch. If you start with a camper shell, you just need to do the interior instead of the shell and interior.
The popup top is the most difficult of doing the inside, but if you follow the directions and look at the pictures, you can do it without much trouble. In North Dakota, I had the chance to sit and talk with Robbie; he had taken a 1991 camper shell and customized the entire inside himself. He talked about the hours he spent and the money, after he was done explaining, I realized he put a lot of time into this project and had himself a great little camper.
Another person from North Carolina had taken a 1992 popup camper and completely redone the interior. It had a different floor plan and everything new furnishings as well as walls and electrical.
I have met a person who used a conversion kit to do a bus. This was a beautiful looking camper when he was finished. Whether people use conversion kits or do it themselves, it turns out one way or another.
The conversion truck camper is truly a sight to see. If you have a chance to see some of them when you are camping, you will want to see the inside. Some camper shows also display truck camper conversions and they have open doors for the public to see just what you can do if you set your mind to it.