Ike, Since I'm the source of the 66 miles let me add a few insights. First realize I hike around a fair bit, I don't stay right on a trail. I go down side trails, I hike down to get water, I hike up a trail to check out a peak. Also I made a mistake and walked down the wrong road for a significant distance. I think it was maybe 3 additional miles. So you might not want to use my distance as the best estimate...unless you hike like me.
Trekking the Southern Appalanchians shows the distance as 54.8 miles with an elevation gain of 16,300 feet. I would say this sounds reasonable to me if you stick right to the trail. What I find to be much more important than the distance is the 16,300 feet of elevation gain. The book shows you how to hike this trip in four nights, three nights, and two nights. I did it in two nights (2.5 days), but had a sub 5 lb base weight and the distance wasn't the challenge the inclines were.
As far as wilderness goes I have not found too many places in the SE where you can hike a 50+ mile loop and not come across a road, building, etc. At the Nantahala Lake you will actually walk down a paved road right past a small gas station selling drinks and snacks. A little further down is a small restaraunt with what smelled to be an incredible collection of country fried foods. And on your right hand side will be boaters drinking beer. Make sure to bring some cash or a really sad face.
You might want to consider the Smoky Mountains for a loop that keeps you away from civilization. But it does have already identified camp sites. If you want a wilderness feeling another place is Linville Gorge, but doing a loop in the gorge is a real challenge.