I know that I am supposed to run a obd2a harness then simply convert a few plugs to fit on the obd1 H series engine. Then use the obd2a-obd1 conversion harness for the ecu.

Well my problem is I do not have a wire harness but do however have a complete H23a harness.... the engine part as well as the part that goes to the ECU. How hard would it be to run a complete obd1 harness in this set-up and what exactly would need to be done to pull this off so everything functions properly?

The only problem I see is getting everything ran properly for the gauge cluster. If it's more problems than it's worth I'll just run a complete obd2a harness with the conversion harness for the EMS.