Can't help, but you've inspired memories of the old A9. These days, parts of the old A9 north of Pitlochry would considered to be of B road standard. Meeting a truck coming the other way could be an alarming experience! I'm pretty sure it was only classed as an A road because it was, militarily, of strategic importance, just like the old A939 - an A classified single-track road with frequent passing places! (With, occasionally, grass seen to be growing in the middle of it !!).