Toronto to Montreal is about 5 hours.
If you want scenic I would drive to Quebec City,
Then follow Highway 40 out of Quebec City eastward till you catch the "Route De fleuve" which follows the St. Lawrence through some very steep grades (18%). Spectacular.
http://www.bonjourquebec.com/anglais...harlevoix.html
Take this all the way east to Baie Commeau and then catch the Ferry to Matane.
From Matane, you can drive Hwy 132 to Point a la Croix and cross into Cambellton New Brunswick.