> ... journals, diaries or letters of those that migrated ...

I don't know of any offhand. The most likely repositories for those would be the libraries where they lived, libraries in nearby towns (such items may have come down through descendants), and the R. Stanton Avery Special Collections Department at NEHGS.

One way you might get a lead on such items is to look up those families up in PERSI and consult the cited articles, looking closely at the footnotes for mentions (and repositories) of diaries, etc. If vital records have been published for a town to which a family migrated, look at the list of private records for items cited in entries concerning the family. Since most VR volumes were published in the century before WWII the locations shown for those private records may be out of date, but you would at least know specific items to ask about at local libraries or NEHGS.

Dale H. Cook, Member, NEHGS and MA Society of Mayflower Descendants;
Plymouth Co. MA Coordinator for the USGenWeb Project
Administrator of http://plymouthcolony.net