Stumbled on an awesome find today. It’s a list of Pre-modern Japanese texts and what translations (if any) have been done. Dated 2013, but it looks like they are trying to keep it updated. So if you are trying to track down a particular early Japanese primary source, this can tell you if it has been translated and where you can find said translation.
You can find it here: Pre-modern Japanese Texts and Translations.
Note: It is a bibliography, so the translations are not hosted. They try to link to articles and such, but how this helps is finding out if some of these primary sources have been translated into English (or other western languages) and finding out where those translations can be found.