The last year should be about 1980; exluding various electronic ignition and timing control modules. Nineteen eighty-one meant O2 sensors for everybody.
As to best, I don't think there is a answer to that question. Even the Edsel, which has probably had more jokes dumped on it than anything, was not that bad a car mechanically.
The problem with Edsel is that is was simply another Ford built vehicle (as a monument to a family member) that duplicated others in the lineup.
A 1980 Chevy would tend to have more problems than a 1970 Chevy simply because the cars were loaded down with more gadgets in an effort to conform with what the Feds were saying had to happen. This is also true of European and Asian cars, although the Europeans had a jump on the fuel injection part of this.
One problem with many vehicles of this era is that many people working on them didn't really understand how it all came together. This usually led to guessing, throwing parts, and making a problem seem far worse than it actually was.