In the old country (Sverige) the name was BENGTSSON. Names of common folk were taken by combining the first name of the father, a possessive "s", and the extension "-son" or "-dottir" depending on gender of the child. Thus, searching genealogy would be difficult, except that the churches of Sweden provided a wealth of information, serving as recorder of births and deaths. If you are aware of what area he came from, it becomes a matter of finding the church, and pouring through archived documents, to identify the family tree.
Very few immigrants made it past Ellis Island with both "S" intact. Seemed extraneous to the folk who processed new arrivals.
BengSTon was also an Ellis Island happening. Whether it was because the agent was dyslexic or thought it didn't sound "American" enough was likely a case-by-case issue.