Hi,
I am also looking for Rankin's in Scotland the link is Agnew/ Wilson/Walker/Buchanan from Ayrshire,so i do not think we are linked but you never know, thought you might like to look these over-----------
John Rankin/Agnes Alexander married 1715 Girvan Ayrshire

Janet Rankin b.31/8/1855, Calton Glasgow parents
Andrew/Elizabeth nee Ashford

Samuel Rankin b.1797 Pennsylvania wife Isabella Ewing

Walter Rankin b.1837 Franklin Tenn d. Nth. Carolina

I am in contact with a lady in the U.S.A who is researching the Rankin's ,the above Walter was her g/grandpa,
Hope some of this is canh help you,
Regards Jean