Hit Points: http://forum.rpg.net/showthread.php?712331-AD-amp-D-hit-Points-What-Do-They-Mean/ No matter what version of D&D I run, I use the Vitality/Wounds concept.
Your wounds equal the higher of Strength or Constitution, and don't increase with level.
Your vitality is determined like standard Hit Points.
Attacks that only take away Vitality can be described as nicks and scraps of even near misses that make you winded. Attacks that get down into your Wounds are necessarily physical wounds.
All Vitality returns at the end of a fight. Wounds heal according to the standard healing rules.
A Labyrinth Lord first level fighter might have:
Vitality - 11 (one maxed d10 Hit Die plus Con bonus) Wounds - 15 (the better of Strength 15 or Constitution 13)
Also, for AC, I say that you get 20 minus your THAC0 as an AC bonus. So a Fighter with THAC0 15 would have an unarmored AC of 4 (unarmored 9 - 5 = 4) further modified by Dex. But this doesn't stack with armor. Take the better. If you are wearing armor, the overlap becomes Damage Reduction. So the above fighter wearing leather would have AC 4 DR 2.
And for damage, I use the ideas of exploding damage dice and follow-through damage from Hackmaster 4E.