Olgar Shiverstone
Legend
i was looking to streamline a couple pieces of BX (E.g.Thief skills and saves) with a target 20 type system. I already convert BX to ascending AC and BAB. So it is not that I am missing anything with BX, it's just that I prefer the more recent d20 type mechanic. Also Next has some pretty good ideas (such as advantage and healing HD) that I could port to BX but before I start porting stuff over I thought I would see if I just do a switch instead.
If that's what you want, pull down Mages & Monsters (free download from here at EN World). It gives you the rules you want, and is more or less compatible with B/X with some minor tweaking.