Well it just so happens that I live just outside of Mountain Twp and was born and raised in the area. Majority of my Mother's family is from Dundas Co as well. There, unfortunately, is not a Genealogical society for the area any longer. I have been told that there are a majority of the former societies' records stored at the public library in Cornwall (of course you could probably find some local records at smaller area libraries too). I also have copies of the Marriage Registers of Upper Canada (1801-1865) & County Marriage Registers of Ontario (Stormont & Dundas 1858-1869) published by Global Heritage Press. If you like, I could do look ups for you.