Can you describe what parts are actually different/swapped? Is there a reason you need OBD1?
Letting us know if you are replacing the block with a D15B, keeping the original Y8 head, or replacing the D15B head with a Y8 version will better help us understand what components you will need to make the swap work.
There is no sense electrically in doing any of what you're trying to do if you already have a D15B engine in there, wanting to go to the Y8 head. Someone already went through the trouble of making the D15B work with an OBD2 engine harness, or it was already an OBD2 engine. Going Y8 head onto an OBD1 D15B is most likely what prompts the conversion to OBD1 if the engine is in fact an OBD1 engine.
You would/should use an OBD2 ECU that runs a D16Y8 engine.
The crankshaft variation sensor mounted on the oil pump of OBD2 D engines is used for misfire detection. Without this sensor mounted and functioning, you will get a fault code if using an OBD2 ECU.
The other issue of converting an OBD2 car to OBD1 is country/state/county emissions testing. If you live in a place where they use OBD2 monitor test result data and MIL light illumination parameter to determine if a vehicle is emissions compliant, using an OBD1 ECU and conversion harness/adapter will not allow the emissions testing equipment to communicate with the ECU, nor is the ECU OBD2 compliant. It would result in an automatic fail, and you would need to remedy ECU communications and pass all monitored tests using an OBD2 ECU to pass emissions testing.
