Old School Microlite20
I’ve just had an epiphany. If you simply drop skills (all four of them) from Microlite20, you should be able to easily run “old school” style adventures very similar to those of “pure” Original Dungeons and Dragons — the three little beige books. Dropping skills from M20 leaves all characters with just their class abilities and their player’s wits which is exactly what you have in OD&D. Sure the rules will be somewhat different, but the feel of the game in actual play should be much the same.