In this teshuva from 1969, Rav Moshe deals with the question of reading from a Megilla that is written in Hebrew but the letters themselves are of another language. In other words, it is written in transliterated Hebrew. He begins by noting that this is a machloket Rishonim, whether we need the language and the alphabet to match or not. He then waxes somewhat philosophical about the origins of language and alphabets, noting that perhaps this entire issue hangs on whether we say that language is a function of the people who speak it, and they have given a collective imprimatur to certain characters to represent only their language, or whether we say that once the alphabet exists, it does not matter what its native users want it used for, and thus it can be used even to write words from other languages. Rav Moshe concludes that Megilla written in Hebrew language must also be written in the familiar Hebrew script (ktav Ashurit).
The teshuva concludes with a paragraph about shnayim mikra v'echad targum, and Rav Moshe rules that when it comes to words who do not have a targum, such as the name of Hashem, they still must be read a third time when one is reading the targum, since failure to read them render the translation unintelligible.