For sheer length it has to be the South Shiel Ridge…I know it’s been done but have zero information.
Here’s some information. Leave the bike at home! You’ll find pics from the ridge which make it look like a goer, it’s a very long day out with very little riding on the ridge but a whole lot of HAB.
That said, the best bit of trail from the day was pushing up on to Creag a Mhaim, I reckon that may be worth an out and back.
The West end into descent in to Kinloch Hourn might well be a cracker too, I’m not sure as I dropped into Glenshiel. That was a carry almost all the way down, a touch depressing…
The ride back up the Glen on the A87 to the van at Cluanie was the most scary bit of road I’ve ever ridden to boot.
One ridge ride I really enjoyed but don’t think it’s oft repeated is the Munros to the north side of Glen Strathfarrar. The riding isn’t on a par with the likes of Macdui and the Lakes, but it’s a proper lovely big day out with plenty of the ridge rideable.
https://www.walkhighlands.co.uk/maps/map3_12ln.shtml