Welcome to the forum
In 1998 PATS was an option in Rangers, not that that matters as far as adding it
1998-2000 Rangers with V6 engines used PATS type B, 4cyl didn't get PATS until 2002
Type B used a separate PATS module located above the glove box behind airbag
The PATS module and the Engine Computer(PCM) are programmed at the factory with a code number they share(see RSA encryption), the PATS module would send a different code each time when ignition key was turned on, and that code would tell PCM to start fuel pump and injectors or not to start fuel pump and injectors
So the PATS module and PCM are a matched pair, they can be re-paired if either fails
There is also a powered antenna looped around the ignition key slot, it sends the keys RFID tag number to PATS module when key/vehicle is turned on
This part is called the transceiver and is not a "matched" part, as long as it fits and its 4 wires are hooked up correctly it can come from any vehicle, its just a powered antenna
There would be a bit of wiring, and you don't need to put the PATS module above glove box, it can go anywhere in the cab, I wouldn't put it in engine bay
Wire diagram below
In it you will see a pink/orange stripe wire last wire on PATS module, it ran to the Starter Relay in the engine bay fuse box
In 1998 this relay is grounded in the fuse box, well just below it
To enable the Starter interrupt you would need to cut that ground wire and hook it to the pink/orange wire, so PATS module could ground that wire if key tested as "OK to start"
Then there is also the Theft Light wire, dark blue/light green, coming from PATS module to the instrument cluster, this is also a Ground wire for the Theft Light bulb which has 12volts all the time
There is no separate harness for this it was integrated into the 1999/2000 dash harness and PCM engine harness
Yes, a kill switch would be much easier, you can "kill" the power to the PCM relay, that disables fuel pump and fuel injectors
I prefer if starter motor works because it makes noise and people notice the noise of a No Start, lol
Another option is the "delay kill", timer circuit that allows start up and drive away but cuts fuel after say 1 or 2 min, when the thief is out on the road, with a DEAD engine, they do not hang around, they run away fast, lol