You're well on track in that I also have it as an ATL Alfa Romeo.
However, thre are differences between the one you've pictured and described and my puzzle car, which from another source gives a somewhat different story.
I'll lock it for you to do a bit more digging (should be very easy) and come up with the story as I have it (although I have to admit there is also a third story around which is different again!!).
Below is another picture of the car you have posted, and you will see some of the differences, e.g. the shape of the rear window, the door handles, the exhausts. Whether my puzzle picture is simply a rebuild of the original or a copy of it I'm not entirely sure. Anycase I'd like to see the story of the car as pictured rather than of it in an earlier guise.