Only found this thread today. Thanks for all the interest in the song. Bob Blair's version of the words is the closest to the original - Archie's is the furthest away, I'm afraid!

Here is "wot I wrote", some time in the 70s:

THE LASSIE O' THE MORNIN'

Oh once Ah thocht the daybreak sun was brichter than the een
As it roused the glen and shook the earth and nestled every geen
But it faded in the warmth o' the brichtest sicht Ah've seen
The bonnie, bonnie lassie o' the mornin'
And the sparkle o' her laughter ever after Ah'll reca'
Like the trinklin', linkin', jinklin' as the mountain burnies fa'
But the hills are empty noo the bonnie lassie she's awa'
The bonnie, bonnie lassie o' the mornin'

The mornin' breathed oot cool as mile for mile we baith gaed on
Reachin' for yon high, high land wi' secret nooks and loans
Whaur the rock was worn and weathered by the friends we'd never known
Together wi' the lassie o' the mornin'
Ower the clouds and through the sun we scrambled tae the cairn above
While the raven soared alow us and the silent words we'd have
And the hills threw oot their airms and gaithered us intae oor love
My love for the lassie o' the mornin'

Then doon the scree we skippit, trundlin', happy on the heel        
We'd fa' and laugh and see oorsels as weans once mair we'd feel
And we baith knew we'd grasped a joy that nane could share or steal
As Ah held the bonnie lassie o' the mornin'
And a dyke across the burn we built tae try tae stop its race
But we micht as well hae tried tae haud oor wild love tae one place
Then Ah saw the look o' paritin'-soon-tae-come cloud ower her face
Oh my Margaret, bonnie lassie o' the mornin'

Bane-weary, wi' one last daft run, we jostled tae the inn
Trippin', grippin', slippin', seein' wha'd be left ahint
Then a gratefu' gasp o' ale, thankfu' for the day just din
And ma ain thanks for the lassie o' the mornin'
A' through the dusk we lingered wi' nae words for us tae say
Nae lang fareweel, 'twould break the spell we'd baith mind a' oor days
Just a tremblin' look, a kiss, a touch – we turned and walked away
And noo the'll never be anither mornin'