Yes it is on 10/10ths. Type in "van to camper conversion" I knew it was a complicated title
Incidentally I saw a very good idea, they had a big Merc Sprinter and because it was their daily delivery van, had made a complete modular unit that they put in through the back doors with a fork lift truck.
You will find it cheaper and less aggro to buy one already done, as we all kid ourselves we can do it cheaper ! The main thing as you will read is the weight and keep the dirty bits away from the sleeping bits !