Safety certificate… from VW for conversion from G60 to Vr6

Where do I get this? Where do I have to call? what do I have to say? Does someone have a number? Fax? Email? What do I have to do to get something like that? I heard that I don’t get the engine remodeling registered… Do I now have a Vr6 2.8l in my Corrado G60… =) Maybe someone like me should do the best? I come from Karlsruhe… know there near a good “nice” Tüv… ??