Disabling Factory Alarm - 92 XJ

I have searched and found so many different methods, I'm not sure which is correct. Can someone tell me the definitive way to disable the factory alarm once and for all? I understand that in some cases you have to swap in a new PCM. I have one from a non-security XJ if that has to be done. So what's the next step?
Preferably I can hear from someone who has actually done it, rather than someone who has a friend who ... you all get my drift.

As many details as possible would be deeply appreciated. Bonus points for pics!
Thx

Are you sure the alarm is actually factory from 92? My guess is that it's an aftermarket add on alarm which will consist of a little box and a bunch of wires tapped to the factory wires. If so pull it all out crimp the starter wire back together if it's been cut and pull out the siren under the hood.

Have had the XJ since 2001. I am absolutely sure. It's a '92 Limited with all options except offroad options. Has a factory fob & receiver in the overhead console. The setup is not the same as aftermarket.

I read somewhere that it's programmed into the PCM so that has to be swapped. But supposedly a new PCM will simply detect the alarm module & rearm itself and back to square 1. Apparently the cure would be to disable the security system before swapping in the new PCM. If it doesn't detect a sec system at the first startup, it will never look for it after. That theory sounds most plausible compared to all the other stuff I've read, but I dunno if that's the correct way.

And that still leaves me with the question: how to disable the system so that the PCM does not see it? Someone on has done this, I'm sure. Please ... a little help! Driving down the road with flashing lights & blowing horn is just not cool.

Well, my info may be useless but my '92 came with the factory alarm but when i bought it there was no fob and i actually didn't even realize it had the system till after i got an aftermarket one installed. So i assumed it just didn't operate since i never activated it.

Sorry i could be of more help.