The set in Johnson's SMM is surely an "earlier sheet music", Mr McLean? As far as I recall, the Pastoral air you mention is actually "The Secret Kiss". I learnt it from this score some thirty years ago, and think it a better match to Burns's words (as well as avoiding the necessary repetition in the more recent setting; same thing as in the "Red, Red Rose" sung to "Low Doun in the Broom" rather than "Major Graham of Inchbrakie"). Good Luck,

An Buachaill Caol Dubh,
Glasgow.