I've included the message here in its entirety. He didn't find any 1970 Census data in digital formatif anyone knows of a source, please let me know. 1970 may be very hard to come by in something called a DIME file. 1990 is readily available. 1980 may be different in some ways then 1990.
Area is northern Illinois.
Any help would be appreciated. Other sources of Census data are also available. They have 1980 BNA files of polygons at the block level only in Metropolitan areas, but for every state. If you would like a copy of it, please email me. I didn't find a source for the 1970 census boundarys.