I don't know if this is what you're looking for but, on the '79 model originally (excuse me if you know this stuff already):
The main fuel pump is different and more expensive than the K-jet cars '80 and on;
The original wiring harness connection at firewall has spade connections. '80 model year and on has bullet conections (no concern unless you're replacing the harness);
The warning buzzer is smaller and won't interchange with '80 and on device (most people take them out anyway);
If manual steering, the ball joints are the same left and right as opposed to distinct LH and RH parts on PS cars (just something to know);
The blower motor is old style - no replacement available but new style works with slight modification to the enclosure (probably has been replaced already);
It may or may not have Lambda Sond system and catalytic converter;
No OD relay, just on/off switch.

That's what I can think of off the top of my head. And some of this stuff may already be changed. There are probably other issues that I can't recall. But '79 is a good year IMO.
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'80 DL 2 dr