Apparently there were some 1979 engines that made it into 1980s cars...?? I have heard on a few occasions of 1980 cars with 1979 style engines in them. The 1980 engine I have cam from a forum member with under 10K miles. Pretty sure it was original to the car.
Luke, looking at the cowl tag, my car had a build date of 09C (3rd week of September). I am pretty sure I matched the VIN number with the serial number stamped on the engine. I looked for and could not find any T stampings on the engine, for whatever that is worth. I think I read somewhere that heads were slightly different on 1980 cars for the air injection system, or maybe the 79's didn't have it? The engine was quiet and smooth running. Not a powerhouse but would give me a little tire squeak from a dead stop.
The engine had 7200 miles on it when removed from the car. I really did not touch the engine other than to replace the original fuel pump, it did not have any issues, but I was concerned that a 40-year-old rubber diaphragm might fail. A previous owner did replace the plugs and wires (did a lousy job with the plug wires). I pulled the rocker covers off to inspect, they were leaking a little oil. With covers removed the engine was very clean, looked like new. I think the factory used RTV, I would use gaskets.