Threaded headset for 1981= mostly in the high 30s in millimeters. My Galli is 19mm on the lower portion.
Threaded headset with the lowest stack height now=? I see some claims of a 12 mm lower stack height, but have not verified.

It was on a bike with a sloping top tube, so it's a little less sloping now. To tell you the truth, I'm not sure I could tell the difference by looking. But if the TT were horizontal, I could imagine you'd notice a visual difference.

My thought is that the fork I took off was too tall to begin with. It is an Italian steel frame which had an American carbon fork. In researching a-c lengths, it seemed that Italian a-c lengths were shorter than most American made forks or at least the one which was on there, so that affirmed my thought that the frame was built with the intention of a shorter fork.

I very much doubt most people can detect a 0.4º change in angle! This is whether the original angle was horizontal or not. It's a tiny amount.