i dont really understand the difference between OBD1 and OBD2, im told its just one wire, but say were doing a swap, can we buy an OBD2 motor and put an OBD1 wiring harness on it?

 

you can put any harness on any engine, but how easy it is changes with every variation.

if you have a 92-95 it's really easy to drop in an OBD2 or OBD1 integra engine.
use the engine harness off of the engine you're working with, and make it work with the chasis harness plugs. (very easy 99% of hte time)
OEM quality and appearance with minimal work.

96-00 civics have a one peice harness so you have to use the harness that came with the car, and they require more work.