I did something similar. I took old photos of Detroit and then went to the same exact spot, took a modern photo, made it black and white and carefully photoshopped the two exactly over one another so\ the comparison perspective was 100% identical. Part of the challenge was asking permission for some views that were from rooftops.

A great start would be whatwasthere.com...which doesn't quite cover Eastern Market, but it's a great resource for before and afters for the other areas as well as Wayne State's digital archives.