I might be able to help. But I noticed a couple of things in the bio you might like to check. The 60th Regiment of Foot was not a British raised unit. It was raised at New York and numbered 60th (Royal American) Regiment. However its officers were recruited from Europe – not from the American colonies – and consisted of English, Scots, Irish, Dutch, Swiss and Germans, but were not British Army officers. The unit was on establishment to the British Army in 1774 and I have checked the Officer Rolls of the 60th through to 1780 but cannot find any Donald Munro.
The bio where it mentions: "Donald Munro born c. 1740; married 27 July 1774 at New York City" might imply that this Donald was in New York already and recruited as part of the recruitment of the 60th. The other Donald may have arrived as part of a British unit.
Are there any other clues you might have?