Johnny,
I would say the first place to start, if you haven't already, is to get a copy of Cornish and Whittens Golf Architecture History book. The first version is called the The Golf Course, and from memory has the best time line summary of the profession. The second version is called the Architects of Golf. Similar, but re-written somewhat in the history section, perhaps for the better.
There have also been recent threads with old aerials of various areas. I think I would download those photos, since if you take a walking tour of any old course, you might not know off hand what was original, changed, restored, etc. The photos would be a good guide to see just how much has changed.