Now, you have it wrong, the difference is that with the K harness, the main differences are the trigger wires, if you look at the chart, in the K harness the main trigger and home trigger signal wires are the same, but the main trigger ground and home trigger ground are not, so, what happens is this, you can use the X ECU with the K harness, but you need to have the trigger and home signals as hall effect so that they only go to pins 6 and 12. The 2 grounds for the trigger and home wires were spliced with pin 26 in the X, which is the main ground.
Also, Ign4 on the X harness is where the home trigger ground wire used to be on the K, but since you are using only Ign1 for your application, that wont be a problem.
Finally, pin 7, the power input in the X, you could open up the connector and splice pin 13, to that one, since i dont know the effects of not having power to pin 7.
Overall, its not really that complicated, since you will have to do these changes in order to use the K harness.
Or, worst case scenario, you have to swap it out for an X harness, the good part is that you dont have to reinstall any sensors, you will be using the ones you already have.
What will you do with your old K? sell it? email me with pics of it.