Putting an S14 KA in my 89 hatch, need a few questions answered

[itslitfam]

Yes I searched things and read every thread, I haven't found answers to my specific questions.

So like the title says, I'm putting an S14 KA in my 89 hatch. I know to put an S13 intake manifold in and use an S13 harness thing but I won't be doing that. Mind you this is my first S chassis, I know a lot of shit but I also don't know a lot (especially anything electrical) of shit so bear with me here if I say something that seems completely irrational, just correct me. The swap I'm buying comes with a harness and ecu from an S14 so if I use those will I be able to wire everything up without an issue? Also what is the difference between the upper, lower, and chassis harness? Like what which harness plugs into what parts? Not specifically, just the area. I'd assume upper goes to parts on the motor like the CAS and manifolds, shit like that. Lower would go to the ECU and trans I guess? And are those two from an S14 compatible with the chassis harness on an 89?

[Aureus Mente]

S13 and S14 Ka transmissions had different bellhousings, The lower harness for the plugs are going to be different. Also the speed sensors for the 2 chassis will be different too. Been there done that with my S14 Auto to Manual swap. Upper harness goes to everything in the engine bay. Save yourself the headache and just do it the right way.

[r20crazy]

seems like u know what to do. but u say not doing that... there is reasons why u HAVE to do that. s14 ecu will not work with s13 harness without alota work, much less guage cluster. bell housings are same, except for auto an manual s14 which have speed sensor hole. if ur going from auto SOHC to manual DOHC (in a SOHC car) u also gotta make a jumper harness. don't reinvent the wheel.... you'll just be kicking ur own ass in a few weeks. chits been covered since day one... save urself the trouble of thinking you can do it when its covered in length that its not worth it. u'll end up spending thousands of dollars making it work when u coulda spent hundreds doing it the easy way... if u got that kinda money to burn PM me, I got this magic water that will cure Zika.... or make u pee a lot.