My family was a member of the congregation in the 1950s and 1960s.I was also a fledgling member of the fantastic men and boys choir.
You may notice the large canyon behind the church that is the New England Thruway Rt. 95. When they were building this route in the '50s the church lost half of the graveyard. Every All Hallows Eve they used to show a homemade movie of the excavation to the choir. Needless to say, some of the grave sites were not the required 100 years old and the film was quite graphic.
I do know that the old grave markers were stored in the basement under the church.
Perhaps you can contact the parish office or priest to see if the markers or records are still there.