Las,
“but can you give me the marei makomos for the Rash, Chidushei Haran and the Mishkanos Yaakov.”
The Rashi is in eruvin 6a (quoted in Igros Moshe) and so is the חי’ הר”ן ס regarding the Ran, it is also mentioned in Teshuvas דברי חיים, מהרש”ם , wherein one rav claimed that once train tracks were constructed all over Europe, that according to the Ran all cities are to be classified as a RhR. All the above disagreed including the בית יצחק ס and the ישועות מלכו of Kutna.
As for the MY, Its an extremely long teshuva, so i will post the page in a later post.