Everything between tha A- and C-pillar resembles the Alfa 75.
But this mock-up is way too old for being related to the 75 project.
So perhaps it is Nuova Giulietta related...but I doubt it.
Might also be a proposal for a facelifted Alfetta.
Note that the door handles are in the style of the facelifted Alfetta and Rio, and Nuova Giulietta and 75.