If you are looking for lists of gunsmiths with information about each, most people would point you toward James Whisker's books, including the one mentioned just above. My own experience of these books is that most of the information is questionable. The author relied heavily, for instance, on earlier publications, such as Sam Dyke's list of gunsmiths, and these earlier publications were simply not accurate. Years ago a series of posts on this forum documented that in detail. I know my saying that will anger people on this site, but I can only report my own experience. Unfortunately, nobody has tackled what would be an immense project: re-checking the information in James Whisker's books against the original records. So we have them and no substitute for them.
In my opinion, the best study of the Pennsylvania longrifle is Wayne Heckert and Donald Vaughn's The Pennsylvania Kentucky Longrifle: A Lancaster Legend (1993). But this focuses on a specific place, Lancaster, rather than Pennsylvania riflemakers more generally--which it sounds like you're looking for.