I'd suggest Rules Cyclopedia. Unlike 1E it has coherent rules for things like initiative, and unlike 2E it doesn't get bogged down in splat. And you can say you're playing D&D, which you technically can't do with the retroclones. And it plays fast, and preps fast. And you can expand the game into domains and strongholds, warfare etc. It's remarkable in some ways that the recent editions of the game have taken significant steps backwards from such scope. I do think something needs to be done about the underpowered thieves, though (either keep them hirelings, or consider using the "autosuccess at DM's discretion" rules on page 124(?) liberally, not needing rolls except in extremis, kind of like the characters that open doors in the Lego Star Wars and Lego Indiana Jones games).
One limitation of it is the splat, and the colour and magic of D&D lives and dies by it's splat. AD&D got the lion's share of the splat by far. Consider supplementing it with the following:
Encyclopedia Magica 1-4 (2E)
Wizard's Spell Compendium 1-4 (2E)
Priest's Spell Compendium 1-3 (2E)
Monster Manual (1E)
Monster Manual II (1E)
Fiend Folio (1E)
Monstrous Manual (2E)
Monstrous Annuals 1-4 (2E)
That right there represents about 20 years of D&D spells, magic items and monsters, but be ruthless in deciding what gets into your game and what doesn't. Amazon and ebay are your friend, here.