One of the oddities of B/X D&D is that nonhuman races are treated as classes. It’s actually a nice streamlining of the fact that nonhuman characters in OD&D were all limited to just one class. All that B/X does is providing separate tables for human fighters, dwarf fighters, and halfling fighters and a table for elven fighter/magic-users.
When adapting the system to settings that are not limited to human PCs something needs to be done to make the other humanoids playable. In the Old World elves are the only race that has stats in B/X and humans don’t exist at all. In addition to that all races can be thieves and witches in addition to fighters. So my solution is very simple: Don’t use special stats for races at all.
All races can be of all classes (no clerics) with no level limits. It’s pointless to make twelve custom classes when I can just use the three classes out of the book. And what difference does race really have for characters? In most editions of D&D it’s almost none and what little there is evaporates to nothing after a few levels.
Though one thing I am currently considering is to create maximum limits for ability scores. Elves are limited to 15 Con, kaas to 15 Dex, skeyn to 15 Str, and yao to 15 Int. But I might even ditch that.