Hello Paul,
I just came across this message trail after looking on RootsChat on a whim. I see it's been about two years since you posted originally, and maybe you have already progressed beyond this. But here goes:
My 3G-grandfather was James S. Strachan (b. 16 Feb 1804 in Forres, Moray, Scotland). I am not sure if this is the same James Strachan you are researching, but mine was married to Emilia Clark (b. 25 Dec 1807 in Scotland) in Forres on 22 Jun 1832. They had a son, James Clark Strachan, in Forres in about 1833 (my 2G-grandfather), and emigrated to Orange County, New York State in the US in 1836/37 via Nova Scotia where they had a second son, John Strachan, in 1836. They had three more sons (William Grant, Robert Hardy and Lewis A.) by 1845.
James S. Strachan (Americanized to Strahan) lived in Newburgh, Orange, NY, USA from 1855 until his death at age 73 on 8 Mar 1877.
I've traced his ancestors ("tentatively" - i.e., I have found evidence on ScotlandsPeople and Ancestry but don't have a lot of corroboration yet) as follows:
James Strachan (b. Jan 1780 in Marykirk, Kincardineshire; d. aft. 1861) m. Margaret Smith (b. abt. 1786 in Marykirk, Kincardineshire).
James was son of John Strachan (b. bef. 1760) and Margaret Clark (b. bef. 1760).
That's as far as I have been able to take it so far. I hope this helps you. If any of this relates to your line, and/or if you have anything to share, I'd appreciate it.
Regards,
Mike