I would go OBD0, for simplicity. It would be easier than trying to convert an OBD2 engine to OBD1, while trying to convert an OBD0 car to OBD1. There's a lot that could go crazy for wiring. I'd just keep the OBD0 and wire it up as that. It's just less complicated to work with. The motor will still run fine, and the ECU will have less to worry about. Just my $0.02, but I really like OBD0.