So you have ridden the GAP/C&O trail(About 330 miles),  and are now looking for some other multi-day rides.
May we suggest some. These typically have one long segment and several side trails, so you might want to consider doing an out and back ride.

Armstrong, Redbank Trails Rosston to Brookville 66.1 side trail to East Brady 4.4 side trail Sligo spur 1.0 side trail Cowanshanock Falls 1.0 total trail miles 72.5 More Details Ghost Town, Hoodlebug Trails Ebensburg to Indiana 43.8 Side almost loop Vintondale to Nanty Glo 13.0 Side trail to Route 22 2.7 total trail miles 59.7 Gasper Caperton, Deckers Creek Trails Reedsville to Fairmont 42.5 side trail to Port Marion 11.3 total trail miles 53.8

Allegheny, Samuel Justis, Oil City, McCormick Trails Emlenton to McClintock Well 38.1 side trail Sandy Creek 14.9 miles total trail miles 53.0 More Details Butler Tredway Trails Butler to Arnold 31.1 side trail to Kiski Bridge total trail miles 37.4 West Penn, Westmoreland Trails Blairsville to Delmont 21.7 side trail North of Saltsburg 2.0 total trail miles 23.7

Assuming that you are comfortable on 1.6 miles of gravel road, and 3.2 miles on narrow , hilly, park road with a short 16% grade hill

Allegheny,Samuel Justis, Oil City, McCormick, Oil Creek, Queen City Trails
Emlenton to Titusville 54.3
side trail Sandy Creek 14.9 miles
side trail to Drake Well Museum 0.4
total trail miles 69.6