The cable goes in place of the rod, and is designed for different carb/intake retrofits on 9xx and 727 equipped cars.
As far as the 4.0 computer is concerned, it needs to believe you have a manual transmission so it runs correctly and doesn't throw codes, since it will not get any feedback from the transmission except road speed.
The AW4 and modern Chrysler automatics both give a certain amount of gear and duty feedback to the computer, but your 998 won't be equipped to do it, so you set up your wiring like you're running a manual transmission, and it will work just fine.
Make sense?