i believe you have Si - is that right? here is what you need to do:
to keep the car as OBD0, the easiest way to do it is to convert everything on the engine to OBD0 - this is what you need to do to accomplish this:
1. Swap the distributor for one from 88-89 Integra.
2. Install a Cylinder Position Sensor on the exhaust camshaft, also from 88-89 Integra.
3. Swap out the injectors for the ones from your Si.
4. Install your Si engine harness onto the ZC and make the wiring change at the distributor. see this:
http://www.zcspeed.com/SiZCwiring.pdf
there are some other things that you will need to do:
1. Remove the engine mount from the driver's side end of the ZC block and remove the same mount from your Si and install it on the ZC.
2. The OBD1 engine has the MAP sensor on top of the throttle body - your Si has it on the firewall - you need to use the one on the throttle body, which means you will need to cut each of the wires on the MAP sensor connector and add a short length of wire to them, so that the connector will reach the throttle body - connector plugs right in.
3. The OBD1 engine has the switch that turns on the cooling fan on the thermostat housing - the Si has it on the back of the block above the oil filter - you need to cut the connector off of the Si engine harness and replace it with the connector that you can rob from the ZC harness - you will need to extend the wires in order for it to reach the thermostat housing.
4. The OBD1 engine uses a different alternator from the OBD0 - you have 2 choices here - you can use the alternator from your Si along with the Si crank pulley or you can install the connector for the alternator from the ZC harness onto your Si harness and use the ZC alternator - i prefer just swapping alternator and crank pulley (the OBD0 uses a 3 rib alternator belt and the OBD1 uses a 4 rib, which is why you need to change pulleys)