Unfortunately, it’s not quite that easy. The last 300 (meaning the blue ones with alloys) seem to have their chassi numbers spread out among all the 1980 96:s. There should be an old forum thread about this somewhere in here.
Found the thread. Swedish only though. The earliest chassi number mentioned for a genuine ”anniversary” model is 96806001982.
So, it’s quite likely the ”last 300” aren’t in fact the last ones manufactured, but a limited series of 300 cars manufactured within the last model year.