When doing research on ancestors, you may find different spellings of their name in various documents. It is only in recent times that the spelling of surnames has become standardized, so the spelling you see in documents often reflects an imperfect phonetic rendering. In addition, immigrants sometimes decided to modify their names after coming to the USA.
One way to deal with variations is to look for a standardized spelling that’s used in Italy today. If you find several possibilities, it can be helpful to look at geographical distribution and frequency. There are several websites that provide such information.
There are two sites that can display maps showing the frequency of a surname in each region of Italy: The Italian Last Names Map has an interactive map with English instructions and information. The GENS cognomi search page is written in Italian, but it’s easy to use and has several nice features, including maps showing surname distribution in the USA as well as in Italy. The GENS search also seems to use a more comprehensive database of surnames.
The Italia.InDettaglio surname search provides an interactive form that can be used to get detailed information about the distribution of surnames within the various regions of Italy. (NOTE: This web page can be very slow to load, so give it some time.)