How to transliterate numerals in non-Latin titles?

When transliterating a non-Latin title into ISO-LATIN-1, how should numbers that are written as Arabic numerals be dealt with?

Should they be left as they are, or transliterated according to how they're intended to be pronounced?

For some examples, should 銀河鉄道999 be transliterated as Ginga Tetsudô 999 or as Ginga Tetsudô Surî-Nain?

Should ファイナルファンタジーII be transliterated as Fainaru fantajî 2 or as Fainaru fantajî tsû?

Should 永遠の831 be transliterated as Eien no 831 or as Eien no Hachisanichi?

Does it make a difference whether the number is pronounced the way an English speaker would expect it to be (like tsû, the Japanese pronunciation of two) or if it's pronounced in a non-obvious way (like Surî-Nain, the Japanese pronunciation of Three-Nine, or Hachisanichi, the Japanese for 831)?

This also applies to Latin characters used in non-Latin titles; e.g., should W3 be left as W3 or transliterated as Wandâ Surî? Or Wandâ 3? Or W Surî?

I've used Japanese examples for consistency, but this also applies to all other non-Latin languages.

I know that both kinds of transliteratations can and should be included as alternative titles (as should one using the correct English spelling of numbers read in English, like Ginga Tetsudô Three-Nine). But I want to know which kind should be used for the origional title field.