Unless you are going to do the conversion yourself, and maintain it yourself or you have a good rapore with the person(s) who fix your van then I would say avoid any form of engine conversion.
If it goes wrong who will fix it?
If you go travelling and it fails who will want to fix a 20 odd year old engine with many bespoke parts and no information regarding the conversion?
It's a common problem that owners of converted vans are up against, often buying vans with alternative engines and no details as to what is under the lid. Clutches, exhausts, cooling parts are often made of a mixture of parts and repairing them can be a minefield.
Just my thoughts on the subject.
