I would like to clarify what I had reported in the name of Rav Moishe Feinstein ZT”L yesterday. In the third Cheilek of Orach Chaim, Siman 5, he clearly says that all havaros that are used by major kehilos in Klal Yisroel are considered Lashon Hakodesh, the proof being Chalitza as I had indicated in my previous post. However, he does also state that it is forbidden for an individual to change his havorah from his mesorah, either from Ashkenaz to Sfard or vice-versa.
In the fourth Cheilek of Orach Chaim, Siman 65, he deals with the issue of a Bar Mitzva boy who is used to the Sefardic havora, and wishes to lain in an Ashkenazic shul with the Sefardic havora. Rav Moishe discourages it, but is matir it “mipnei hasholom” provided that a second minyan is made in a second room in the shul where the sedra will be lained with the Ashkenazic havora.
It is not clear from Rav Moishe whether or not you are yoitze b’dieved with the kria. Maybe you are, as he states that the Chalitzos of Ashkenazim are valid for Sefardim to rely on and vice-versa. But from the two tshuvos that I had mentioned, it is clear that he does not l’chatchila approve of a Sefardishe Kria in an Ashkenazic Shul and probably not vice-versa.