GSL-SE conversion on SA. Wiring
 

The SE EFI engine is going in my 80. So in theory you should be able to drop the SE engine right in with the notched bracket and right header. The main engine harness powers everything on the engine and connects directly to the ECU. The ignition, headlights, horn, radio, blower (body electrics) should not change right?

My concern is what do I do with the two connectors right off the ECU? I assume they connect to an under dash harness on the SE that taps into the interior fuse block to send 12v to the ECU and the fuel pump relay. Without the SE under dash harness where do I start?

you need to look at the FSM, and they will list the connector (x15?) and then you will have to look at the diagram to see what each wire does.

off the top there will be a b+ battery power, a switched power, a wire for "start", the wire from the coils that gives RPM, the fuel pump wire, all of which you need. there will be cruise control on there too, i think, and then there is probably something else too, although i'm not sure what.

the 1980 has an emissions control unit where the -SE ecu would go, so it should have the power wires, and probably the tach too.

the best way is to make a little harness that plugs into the car, and then plugs into the harness, so you don't have to cut much