now it's me not receiving notifications....well, I've been trawling through the church records to find my huband's ancestors (who started in Rovigno then moved to Orsera and are now in Pula. Except for us who are in London

and both the surnames pop up a million times. It'd be great fun I think to see how far back you can go. Does your dad speak any Italian, still? (dialect?) Because the Comunita' degli Italiani is quite helpful and active (or at least it was active when I went there the first time years ago), they have LOADS of information. See here:
https://www.facebook.com/ciztrovigno
Both families were living in Rovigno and in Orsera, I have seen recently the tombstones of Quarantotto in the old cemetery in Orsera, the association of the 'esuli' also put up a stone in memory of those whom emigrated etc etc. It is quite a moving thing. I really think your dad would actually like to know that even if Italians have left, there is still a community going, the language is spoken, there are Italian schools, clubs, libraries, now that croatia is part of the EU there is also a less of a feeling of boundaries.
I've managed to find information from the 'catasto' (the town planning record) for Orsera, some families have names recorded in the maps, it might be possible to do the same for Rovigno but the easiest way is to ask the Comunita', also because there were really DOZENS of Quarantotto and Malusa'
I'm happy to help, if you need anything. We have actually gone to Istria over the summer, fingers crossed will go again in the spring...