I've sent the pictures to the Iso-millennium site and they returned me this e-mail today:
Hallo AlfaRonny, I have showed the pictures to my Iso Millennium Committe friends and we believe this is an "unofficial" replica of the Ferrari BreadVan built by Giotto Bizzarrini on a GTO chassis. It can be a recent model, built by an extravagant coach-builder... thank you for the pictures and best regards!
Iso Millennium Committee
So no definite identification of the mystery car.
Maybe someone will react later ???