KNAVE is now my favorite OSR "Rosetta Stone" system. It's primarily aimed at the player-side of the game, with character creation rules, combat, advancement, and gear, but there is a brief section on magic that covers magical treasures, as well as monster conversions that covers most of your needs across every bestiary good for just about any OSR game, from ODnD to ADnD and beyond.

It's missing worldbuilding and scenario building materials, as well as example monsters, but it's assumed you're supplying those from your favorite source(s) and can therefore build whatever assumptions you want into the game. The key is getting the player-facing material all "on the same page," and for that Knave is perfect.