OSR Hit locations for Ascending AC

METHOD:

• Natural d20 die result, when successfully hit with to-hit bonus, also determines the hit location.
• Natural 1 die result is always a fumble (determined by DM or other optional rules).
• Natural 20 is a critical hit with other optional rules.
• Results 2 and 12 let the target hit to choose the hit location.

HP DISTRIBUTION (optional rule):

• Every damage from a successful hit is reduced from character's hp value.
• The damage is also reduced from a hit location.
• Hit locations have individual hp based on character's hp value (normal rounding rules, minimum 1).
• When a hit locations hp is reduced to zero, that body part is incapacitated. Healing takes one week per negative hp.
• A save versus death must be made every time a body part with negative hp suffers damage. A save is made in a penalty of negative hit points of that body part. If the save is unsuccessful, that body part is lost. If head, chest, or abdomen is lost - you die.

HP DISTRIBUTION EXAMPE:
Bermund, 3rd level Fighting Man has 13 hit points. His hit location hp would be:
Head: 3, Arms 7, Chest 9, Abdomen: 7, Legs: 4.

COMBAT DAMAGE EXAMPLE:
Orc swings his axe at Bermund with roll result 17, hitting him at chest. The damage is 4 points, so Bermund's total HP is reduced to 9 and chest's HP to 5. Next blow hits his right arm with die result 19 dealing 5 damage. His total hp is reduced to 4 and right arm's hp to 2. Third hit strikes the right arm again, dealing 3 damage. Total hp is at 1 now, and right arm at -1. Bermund rolls d20-1 to save, and fails. His right arm is chopped off.

COMBAT HEALING EXAMPLE:
Bermund's right arm doesn't heal, as he doesn't have got it any more. It takes one week though, to bring the stump from -1 back to 0. After one week, his stump of a right arm is healed.
His chest is healed in five day's rest and he is back to maximum 13 hp after 12 days of rest.

BONUS: ALTERNATIVE HIT LOCATION DISTRIBUTION:
+Joshua Fox at Google Plus suggested these hit locations saying:

I'm not an expert, but I recon the fighter works hardest to protect their head, followed by their body. Their arms are constantly exposed to danger by attempting to strike their opponents or ward off blows, and the legs are just a bit harder to protect given you're focusing on the head and body.

So I'd say something like

• 20: crit, attacker's choice
• 9, 12, 19: sword arm
• 8, 11, 18: offhand arm
• 2, 7, 17: leg on same side as sword
• 6, 16: other leg
• 5, 15: abdomen
• 4,14: chest
• 13: head
• 1: fumble, and defender's choice 

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Disclaimer: I haven't playtested this. So I have no idea if it works or not! I suggest you only let player characters use this as counting hit location hp for all orcs and skeletons is a lot of work. Just describe how they suffer!