Warriors of the Red Planet is basically the only OD&D based one that doesn't deliberately suck in order to be "Older School than Thou".
It uses ascending armor class, but it doesn't used the severely gimped attack bonuses as in other OD&D. Warriors go up +1 per level. Which makes sense, the game is based around a d20 and AC goes from 10 to -10 (or 10 to 30) and none of this AC9 BS.
Similarly, it has hit dice that are full, actual dice of varying size depending on class. None of the 1d6+2 HP crap.
Has a unified ability score table (from B/X)
And none of that single saving throw BS. Too bad the other Night Owl Games go the Older School Than Thou route and thus suck. But they were designed by different people.
Spears of the Dawn also does all of that, it's more modern in other ways though, like having the Sine Nomine skill system (based more on Classic Traveller).
Crypts and Things 2.0 is also pretty good, probably the best sword & sorcery style OSR game. They replaced the single saving throw BS with a luck attribute from Fighting Fantasy which works pretty well.