probably just a 1mm spacer for under the fixed cup and let the adj. cut fall where it may. Doesn't hurt to have a selection of shims so you can try-and-err, they usual come in 0.5mm and 1mm thick, don't know if they make them in 36mm ID for Italian cups or not, but if you have to clip them to fit the larger diameter, they still will work as shims.
The shell may have been "aggressively" faced and somebody ground away that much steel, but could also have been re-tapped from BSC to Ital.