I have typed up my armor classification notes below for use in any old school (original or retro clone) version of the game. (Not using d6 as outlined in my initial post - just base AC). You can download the document here (or in my downloads sidebar).
I am working on my own game for my Under-city megadungeon based mostly on the LBB OD&D. I am removing the cleric class and replacing it with a non-spell casting Templar class. The magic-user is being replaced by a "Sorcerer" class that has access to both cleric and magic-user spells.
I have already written up the Templar and hope to post more about it soon.