My personal O/AD&D shitbrew

After delving into old school TSR-era D&D rule systems and dealing with some frustrations while playing sessions "by the book", I've come to realize that I prefer a synthesis of OD&D and AD&D for my games. By far the best supplement for OD&D is the AD&D Dungeon Masters Guide, which drowns the reader in rules that expand on and explain the ones introduced in the OD&D LBBs. The Players Handbook, on the other hand, basically replaces material from Men&Magic, by expanding class and race options and increasing the numerical inflation of all ability scores. It is specifically the numerical inflation of character abilities in the PHB that is my issue with the system, so instead of that book I will be relying on Men & Magic.

My personal canon of books would be the OD&D 3 books and Supplement I: Greyhawk, using all the options from all 4 books. That includes the Thief and the Paladin, Demihuman multiclass options, percentile strength charts, Magic-User chance to know spells, variable weapon damage, variable hit die, and monster XP determination. The Monster and Dungeon levels tables from Monsters & Treasure and Greyhawk will be used (really who needs more than 6 dungeon levels?), but just for kicks I might incorporate material from the Monster Manual because all of that content is directly compatible and was basically written for OD&D anyway.

Combat is probably the thorniest issue of Original and Advanced D&D. OD&D actually doesn't have a combat system, just a chart describing the use of a d20 to replace Chainmail's hit determination matrix, and for everything else it refers the reader back to Chainmail. Since the d20 has become the standard for D&D combat, I'm more inclined to use that system, and the one time I played with Chainmail's combat as written our group quickly abandoned it for being too complicated. I am a fan of the 2d6 system though, it seems more similar to hex-and-chit board wargames, so depending on what dice I have at hand I might use Chainmail's system. The default combat system in my games, however, will be AD&D's combat sequence with the to-hit matrices and weapon damage charts from OD&D. I have found a use for the weapon vs armor charts and plan to use them, but only if player characters start becoming unreasonably hard to hit, and only the weapon vs. armor from OD&D. There is no reason for the ridiculous list of polearms from AD&D or the negative Armor Classes.

So where at all possible, material from OD&D will be used, including the additions and changes included in Greyhawk, and the AD&D DMG and Monster Manual will be used to fill in options and provide extra material when necessary. This keeps the simple and easy to use systems from OD&D, except in the cases where they're not straightforward and easy to use, and then material from AD&D will be used to supplement it. I figure this creates a complete ecosystem in which to play which shores up the flaws that both games would have separately, and yet retains the spirit of something that is recognizably D&D.