You can get all of those engines at Bruckner Hobbies. The Mr-12 is stocked at Harco Hobbies, but is currently out of stock.
http://www.harcohobbies.com/nitro-rc-engines.aspx
http://www.brucknerhobbies.com/Nitro%20Engines.htm
Tower hobbies has a wide selection of engines, but I would only consider the Novarossi / Trinity section for touring car engines.