I agree that the car is from 1993, not 1983, but still, it looks very similar. As you said, very different rear wing, modified front section, more refinement on air guidance, cooling and ducting. I also agree that the factory single element rear wing was very rudimentary in its concept and that there is large room for improvement, but that's still a big number.
Although as you also said, other teams were well above that value, which I find really impressive. I doubt that they were able to reach 200mph with their engines tho, even if they were powerful. But impressive indeed.
A similar version, look at that profile, that looks very aggressive, I love it: