Hi Jean,
I remember looking for your people before. However, I don't remember
what I suggested (if anything) at that time. Searching for ancestors that
were Catholic in Hannover is extremely difficult. They simply have not
allowed their records to be microfilmed by the LDS. So, I have a couple
suggestions:
There were 2 census of the archdiocese of Munster (which would cover
most of the Catholics in the Hannover area in 1649 and 1749). Look at this
website which will include information about that census and give other
suggestions for your search:
http://www.emslanders.com/sources.htm#Emsland%20Chruch