After I've dropped several projects of mine, finally I've collected the House Rules I've used in Swords&Wizardry my science-fantasy campaign (but you can easily use them with Labyrinth Lord).
Basically that's what they do:
- They allow you to make custom classes (like Thief, Bard or Paladin) starting from the six core classes (Fighter, Magic User, Cleric, Halfling, Dwarf and Elf)
- They use a roll-under resolution for combat (with a descending Armor Class), skills and saving throws
- There's a revised system, still pseudo-vancian (same old spell slots) but with a more talislantan-style approach (spells created on the fly and possible mishaps)
Enjoy it. ^_^