Hi,
John McDowall is listed as an ag. lab 20 at Culgroat, Stoneykirk on the 1841 census, there are a lot of McDowall's listed, will try to see if I can find if any were his parents.
Also listed is Martha Morrison, 10 with her parents and siblings, I can give you both lists if you want them, also her brother Abraham and Susan Morrison, who later got married, there is a death entry on the 1855 list for there son James.
Let me know if you want the info.
Regards
Beannie