We know that in scholarly work we generally do not translate personal names from Italian into English, but make an exception for historical figures and ancient writers and thinkers. For example: we would anglicize 'Aristotele' to 'Aristotle' in an English translation, but we would leave the name 'Maria Montessori' exactly as it appears in Italian. We would definitely not change it to, say, 'Mary Montessors' in an English translation.
Let us now focus on the exceptions to the rule. Sometimes we already know from our education or past experience. For instance, I know that 'Platone' is 'Plato' to English speakers and 'that 'Giulio Cesare' is 'Julius Caesar'. However, the other day I came across the Italicized name of an ancient Roman I did not recognize: 'Arpocrazione'. It was clear that this ancient scholar was not exactly a household name in the modern world. So how is one to find out whether or not he has an anglicized name and what it is?
First, I typed 'Arpocrazione' into a popular search engine, and clicked on the Italian Wikipedia result.
Then, I scrolled down and found the 'English' link under the 'in altre lingue' subheading, which can be found on the left-hand side of the page.
That link took me to the English version of the exact same page. The description on the page was indeed consistent with the context concerning this same grammarian in the article I was translating, and the title of the page informed me that he is known as 'Harpocration' to English speakers.
You may notice that there are certain patterns here: 'i' at the end of a name in Italian becomes an 's' in English, 'a' at the beginning of a name in Italian is generally preceded by an 'h' in English, etc. Keep in mind, however, that there are many exceptions and that there may be different ways of rendering the same name in English. The Russian author, whose name in Italian is usually spelled 'Dostoevsij', can be either be spelled 'Dostoevsky' or 'Dostoyevsky' in English (the English spelling--or the spelling in any target language--that you choose will depend on factors such as which usage is more common, your client's preference, or their publisher's preference).
Unless you are absolutely sure of the anglicized spelling of such names, always make sure to verify. It is best not to risk embarrassing your client when it is so easy to look something up.
My hope is that this method makes it even easier for you to do so!