I am the leader of the Clan Donald DNA Project. W've in the past thought, based on several claims similar to yours, that we had a Y-DNA profile for the Kinlochmodart chieftain line. But now there are competing claims to that profile (Morar) that seem at least somewhat better. But we still have that list of Kinlochmoidart claimants. If you have a close all-male-line brother, uncle, or cousin in your line a test might possibly be of use ... but it has to be the BigY700, which is rather expensive if it genberates nothing useful, which is say a 60% probability.
Doug McDonald