Hey Rick -
I have Croatian ancestors through both of my grandmothers. I have had a lot of success finding information on them in the church books from Croatia that have been digitized on FamilySearch:
https://www.familysearch.org/search/collection/2040054
My advice to you is to not try and do a name/surname search for this, as only a very small fraction of the 1.5 million images in this collection have been indexed.
Instead, go down to the bottom of the page to:
Browse through 1,421,761 images
This allows you to look at the records by religious denomination - then, within each domination, the records are organized down to the parish level. I was able to find several of my various family lines through the parish-level records.
Let me know if you have any questions. I got to be pretty familiar with this record set a few years ago.