I coud not find "Basso as a Sephardic nane" in any list. I live in Spain and we really thank yopu if you can send to me information where cand I find this surname. I have found a lot of Bassos in Cataluña. I have a list of investigations of Mormons in Spanish churches and there were Bassos in Spain in the XVI century. But I allways believed that the original Basso cames from Italy and not, as you said, from Spanish Jewish.