i was wondering if i switch my stock carb dx motor in an 87 sedan with a motor from a 87 crx si or civic si can i use the original wiring harness, ecu, and tranny

 

If you want to keep the Si motor MPFI then you will have to covert your car to fuel injection. That means replacing most of the wiring and all of the fuel system. This is one of the most difficult swaps you can do on a Honda.

The tranny will bolt up though

 

So if get the wiring harness and ecu i can do it or is thre more????