I love a long bed 1st gen. With the long bed you can actually use it as a pickup. Wheel base is nice for high speed dirt and climbing too. If you still think it's to long bobbed long beds look sweet.
The 20r is a great engine. Head flows better than a 22r, so what you lack in displacement you make up for in cylinder head. When the 4 speed grenades slap a 5 speed in it. When I got my '80 it had the 4 speed and I got 22 mpg on the interstate with it after a tune up.
When it comes to 1st gens, get what you can get. Long or short they are vastly superior in many little ways. '79 and '80 are my favorites.