Its been acouple years since I put a JDM 89+ in my 87 so I'm going on memory. The JDM had a cut harness so I had to use the 87 harness . I think I only had to use acouple of the temp sensors off the 87 and the cps (wasn't sure because of the differt colors on the cps ,have since saw a thread that the cps is the same just different color plug. )
NO, all that you need to do is swap all the sensors from the 87 onto the 89, so that they match your harness. Swap the motor mounts to match your chassis, basically mock the new motor up just like what you pulled out. Use your same wiring harness etc. that is currently in the car. The car doesn't know what year motor you put in it.
Also, double check the injectors, I think they may have different connectors, I cannot speak from experience on that one.
well i me and sash did it all last night,all we pulled the motor out the 87,and the 89t was complete with harness and all,so all we're doing is pluging it and go,i already swapped the motor mounts also,so hopefully it cranks up tonight,wish us luck