I have Census BlockCode information (15 digits) and need to get corresponding street name and address in NYC. What is the best source of such information?
NYC should have a data warehouse that will have census block information. If it were me I would probably find that data and make a nice map with point locations through QGIS, but I just looked it up real quick and found this link.
You can look up census tracts or by address, and make sure to zoom about 50% of the way to view the census tract numbers.
Census data is something that is open to the public, I am from San Diego and we have an organization called SANDAG that houses all of the public GIS data. There should be a government website to reach that can fit your solution if this link above doesn't