Mountain Township is now an amalgamated township in what is now known as North Dundas Township, Dundas County, Ontario, Canada. As for your St Andrews Presbyterian Church, the only one in that denomination is located at 34 Mill St.,
Chesterville, Ontario. Many of these records can be located through Ancestry.ca but you could also try contacting the church (if in fact this is the correct one you are looking for) at (613)448-1304. If you could narrow your search down to a specific village it might help as well as people didn't tend to drive very far to attend church. What families are you looking for info on as I have many branches in this area?