Here's the thing, as much as it may not be approved of by many folks, there simply are not any "overlanding" routes anywhere east of the Mississippi river. There are however a handful of places left to go "four wheelin", which, if we aren't careful will soon be closed down. ( think tread lightly, leave no trace, ethics)
The best we have in the east is found up in the Maine backcountry, where you can become lost for weeks if you don't know what you're doing. Everywhere else it is a patchwork of state or national forest roads where one can pretend they are "overlanding". The only state/national forest I know of that has rustic dispersed car camping is in Pennsylvania that does not even require a four wheel drive vehicle. There is however, a varied network of maintained and unmaintained forest roads that can be used to move from campsite to campsite, depending upon what kind of vehicle you choose to use. It is my understanding that up in Maine the back country is privately owned by the lumber companies. One pays a fee to access the land and explore it by vehicle. We have camped in the southern sector of the National Forests in Virginia and were sorely disappointed at the lack of "overlanding" opportunities to be had there. Personally I cannot wait to move west, where fortunately, one can still find a bit of solitude. I hate to throw a wet blanket on your search, but it is what it is. When public lands are carved up with private lands, (think NO TRESPASSING) "overlanding" opportunities are non-existent. (you guessed it, I'm a strong advocate of keeping public lands public) Good luck with your adventures.