Looking for Robert Cowan and Eliza Gunstone of Quebec City Prior to 1833

I have done considerable research over many years on my Cowan ancestry. The earliest record is the 1833 marriage of my great great-grandparents at St. Andrews Church in Quebec City. They are Robert Cowan and Eliza Gunstone who, according to census records are from Scotland. I have no record of siblings or parents, immigration and homeland in Scotland. Dumfries or Ayrshire are likely. I have several hundred pages of genealogies and stories accumulated and recorded on my website http://www.cowangenealogy.weebly.com