Adventure Cycling's Transamerica route passes somewhat near (about 60 miles) Bowling Green, KY, and there is a spur to Mamouhth Cave, which takes you even closer to Bowling Green. You could hook up with their Atlantic Coast in Norristown, PA (where is crosses the SRT) and take it to the intersection with the TransAm in VA. The convenience of this approach is that services (camground, grocery stores, etc.) are shown on the map.