AD&D is a game that (despite the rulebook's insistence that there is a correct way to play and an incorrect one) has always been houseruled. Even when I was younger and didn't understand all of the rules, I just ignored what I didn't get--which, I suppose, is a type of house ruling. So in the light of that, I thought I'd offer some brief notes as to what I'd change in AD&D.
Not using the armor vs. weapon type table.
No weapon speed factors.
Using the revised Monk and Bard Classes from The Best of Dragon vol.III.
Ignore the unwieldy hand to hand rules from the DMG.
Not using weapon proficiencies.
I'm going the keep the prices and coin from the Player's Handbook, but in practice I'll likely almost entirely ignore electrum and platinum pieces.
Characters make attribute checks by rolling their attribute or lower on a d20 for class attributes. Non-class attributes are rolled at the attribute minus 4.
Things I'm unsure about:
Not sure whether I'd want to use the classes from Unearthed Aracana. I like the idea of Barbarians and Acrobats, but the rules seem increasingly fiddly.
Not sure about casting times. I might just adopt the OD&D/Basic D&D method for casting--which is basically that spells take place instantaneously.
I'm by nature a lazy DM and much of these rules are me just trying to shape the ruleset into something that I'd feel comfortable running.
Here's the character sheet I made: