It's not necessarily the case that your Tuscan-born ancestors were actually French.Below is a note from the website of St. Matthew Roman Catholic Church in Monroe, Louisiana that explains why many sacramental records were recorded in French, with French versions of names recorded no matter what the national origins of the individual.
"A word about language: in this area we did not have native born clergy. The priests were generally form France and they recorded the sacramental information in French. Most of the earliest records require translation. Prayers, sermons and instructions in Catholic schools also were in French while most of the population was English speaking. It wasn't until 1878 that the Bishop required everything to be in English. Another characteristic of recording of baptisms had to do with French speaking priests writing down names that were Spanish, English, etc…and misspelling them or because a first name was to be that of a saint, adding the first name of "Mary, Marie" or "John, Joseph" in front of the individual's actual name. Sometimes the priest was the only one present who could read and write, so no one could verify that names ere recorded correctly. "
So, in Louisiana for much of its history, all records were recorded in French.Your ancestors are likely true Italians whose records were officially recorded by a French-speaking priest, in French, with French spellings of the names.