I presently working on Ayrshire Galt's my own John Galt and Agnes Guthrie from Irvine.
I am also looking at other Galt families and have just started puting them on computer.
Regarding James Galt and Agnes Harper - I do have some more info.
I have info on their children
Some of John Galt and Elizabeth Wright's children were born in Dreghorn. Where they married in 1763.