Well a '79 or '80 is good because they will have 4.37 ring & pinion gears and the 20r head is also nice, but these have a weak 4 speed, which is no big deal becasue you can swap in a 5 speed later.  '79 and '80 are my personal favorite for some reason. With the 4.37s you are good to go for 31s and can even get by OK with 33s.  Little things like solid spacer sleeves on the pinion instead of crush sleeves, steering slip joints and u-joints where later years have rag joints kind of set these early ones apart in stock condition. I feel the 20r carb, while gutless works better on it's side and vertical than the 22r carb, but that just may be my experience.

An '81 is cool because you are guaranteed to get a dual row timing chain 22r that you can make into the 20r/22r hybrid for a hot 4 banger, and an OK 5 speed, but they have 3.90 ring and pinion gears, which really sucks for big tires, not a real problem if you plan to re-gear.

'82 and '83 have a more realistic gear ratio with 4.10s, 22r and a decent 5 speed and square headlights.

You can't really loose with any 1st gen, but '79 and '80 are my favorite in stock form.