The Westfalia camper is custom-made at the factory. Conversion of a standard Vanagon requires removing the welds from the roof of and existing camper and moving that entire roof to the vanagon, not just the fiberglass camper top. This requires a high level of skill and experience that most people don't posess. It also requires a complete donor vehicle. The interior must be moved over as well as hols cut into the side of the "new" camper to allow for the hook-ups/fill-ups on the driver side.