I purchase most of my meat at Chez Vito 5180 St-Urbain, corner Fairmount. It's not THAT far from CDN if you just go over the mountain.
I also think they have really good butchers at the Atwater market. I have bought everything from ribs, brochettes, steaks, veal hot dogs etc.
I am not Kosher... but I do prefer the taste of kosher meat. I am always satisfied by the meat I buy fromJ& R Montreal. kosher beef, veal, lamb and chicken. They also DELIVER anywhere from CSL to Downtown ect. Orders must be over $100.
See the Great Butcher Shops thread: http://chowhound.chow.com/topics/555714
My favourite source for beef in CDN is Boucherie de Paris (5216 Gatineau, 514 731-6615).
Pork ribs, especially baby back ribs, are not exactly a Quebec thing and so are harder to find, though that's slowly changing. You might try Porcmeilleur at the Jean Talon Market. The few times I've made them, I've ended up buying them at Loblaws.