I am looking for some information on what i believe use to be an OEM replacement head for the 2300's. I've seen a couple of pictures of one that was called an "M13" head. It is an oval port head with the heart shaped, closed combustion chamber. I'm looking to find out who and when it was manufactured and if it was ever sold on any production cars and if so, what year and model. I've been told they came on turbo coupe mustangs and some rangers but i have searched and have for no evidence or information to support this. Any help or information about this head would be greatly appreciated. Thank you in advance.