Doug,
I'm a planner too. Right now I am putting together getting to Patterson LA in the spring and Rapid City SD for the fall rallies and then what comes between??
I am going to suggest that you look at picking up Skyline Drive in Front Royal VA and run that to the Blue Ridge Parkway. This will take some planning as there are some low clearance tunnels on the BRP. I don't remember them because I only need 9' to be good. BRP will end in Cherokee NC.
From there, it is about a full day (~300 road miles) to the head of the Natchez Trace. You can take that to Natchez(Duh?) and have a stop along the way to tour Vicksburg. There really is an historical marked about every other mile along the Trace. You need to find the book.
From Natchez you can do a river crawl as far south as you like and then head back along the gulf coast. I can't even remember all the museums, but Mobile and Pensacola Naval Air are a given.
There is enough else to do between there and Maryland that I am sure that you can find something to do on the backhaul.
Matt