Another for the filing cabinet: The small -radiator- fan motor (used on the left side of the radiator, here I do not mean the AC condenser) is a Magneti Marelli MTX4AA, listed for Autobianchi Primula series I. You may not have found one in your box of Autobianchi parts...
See also what a Maserati Quattroporte Series 1 fan and motor look like...(and well, this is probably the exact setup used on very early Mangusta, using the squarish Lucas motors. These were changed to the round Lucas motor on the right and this Marelli motor on the left)--Lee