Hi Teresa -- thanks for posting to History Hub!
We checked in the CIS Indexes, which index all published congressional hearings, and unfortunately don't see that a William J. Tansey testified in the late 1950s. We covered the 82nd to 87th Congresses (1951 to 1962). The only 'Tansey' listed is a 'Joseph Tansey' who testified regarding juvenile delinquency in the 83rd Congress.
Generally the best resource for finding congressional hearing transcripts is ProQuest Congressional, a subscription database. I'd recommend checking with a local academic or law library for access to ProQuest. Congressional hearing transcripts are often available online through sites like Hathi Trust, Google Books. and the Internet Archive, which I'd recommend searching directly.
If you have more information about the year and which committee (or subcommittee) heard the testimony, perhaps we can continue the search in our records. You can contact us directly at the Center for Legislative Archives via email at email@example.com.
You also might want to contact the Margaret Chase Smith Library, which holds her personal papers.