Surname: Drummond, McGregor

Gregor DRUMMOND m: 1768 to Margaret MCALPINE in Callendar Perth. Searching for Gregor Drummond's parentage. Married with surname of Drummond, changed surname to McGregor after birth of 1st child, Patrick c: 15 Nov 1768. Other children, John c: 25 Dec 1773, Robert c: 5 May 1775, Alexander c: 12 Jan 1777, Catharine c: 15 Feb 1778, Robert c: 7 May 1780. All children born in Callendar. Alexander m. Margaret MCLEAN and had son John c: 15 May 1803 in Aberfoyle, Perth.
We are related through Alexander.
It is possible that the aforementioned Gregor (Drummond)McGregor married Marjory or Margaret Drummond at Callander (28Dec1750). Their first child looks like Donald born 12 bapt 17 Mar 1751 at Callander(OPR). Then Coll born 9 bapt
12 Jan 1755, Callander. The mother for these two was Margaret McGregor and the address was Dreppan. Then Gregor McGregor and Margaret McAlpin had Patrick born 11 Nov 1768 at Coillbeg, bapt 25 Nov at Callander. The other children stated above fit in with these.
Rob Roy's son Coll had a son Gregor born about this time. I have been referred to the papers of John McGregor WS at the Scottish Record Office. Their reference is GD50/184/84/5 which should lead to the very piece of paper I want. I am in the process of obtaining this reference but am interested to see if any one else is looking for the same info.