Body conditioning is something you might want to be careful with. Chances are that you'll create problems that will return later. Chronic pain stuff and malfunctioning joints and so on, all depending. Toughening the skin, and desensitizing the local nerves might be safe, but be careful with messing with bone and hard contacts. I don't know if it's accurate but the story about Mas Oyama's conditioning catching up on him in old age supposedly had him in such a state that he couldn't even have his hands under the bedsheets at night. in short, there might be a price to pay there. The shaolin people supposedly had some extensive herbal medecinal course they went on along the steps of their iron-whatever conditioning to prevent arthritis and nerve damage as much as possible, but I'm not much familliar with that.
I seem to remember having read something about the experience of pain being something like 70% psychological, and at least my experience with how pain seems to feel in different states seems to corroborate that. This is something that might be more immediately useful to you. You could say that with the whole psychological/emotional processing of pain you FEEL pain, in the fullest sense of the word. Without slapping emotions, and a story on it you simply seem to REGISTER it. For lack of a better term you could call it a tough state of mind. Very much related to getting staying-power into your mental state. Maybe I should explain...
It seems like the combative state needs two things.
1) Aggressive state. very eager to smash, bash and break people. Bloodthisty and sadistic and all that.
2) ...the "tough" state. You might call it having "heart." Willing to sacrifice, willing to risk and expose yourself to the pain and damage-potential of the fight. Pretty common stuff that makes a regular appearance in warrior ideology more or less across the board. Hagakure for instance. Also reminds me of that Bruce Lee vid that was posted here some time ago; "You need to learn the art of dying."
(It's interesting to note that both of these are pretty dysfunctional under normal circumstances. #1 is psychopathic and #2 tends to be depressive and bleak. But they're perfect for dysfunctional situations. Also a bit of a warning to use with care. Keep the monster on a leash.)
On the NLP side of it, taking the third position - dissociating - as if imagining looking at yourself from a camera or something a few meters away. Another method is to think of your body as a kind of machine. Using medical and anatomical terms might be very useful here I think. It's both true and useful to know, plus you get the distancing and abstracting effect from the terminology you're using. The sensation becomes more like seeing a warning light on the machine telling you the machine is running outside of recommended parameters than the common sensation of "pain."