Just wondering what needs to be done to put a k24a8 engine harness into my 04 ep3 with k24a1/k20a2.

 

you should be reusing the original harness from the car

 

To put a k24a8 engine harness in your car you would most likely have to repin the ecu connections. So if you good with wiring there you go. If not then do what dood said just use the k20a3 harness that came with the car. It is much easier.