Like you said, you can't find any other examples where identical chassis with 2 engine choices, in the same class are listed on multiple spec lines.
[/b]
But I did find several cars that have multiple engine choices, in the same class listed on SINGLE spec lines. What is the justification for the Neon to have multiple spec lines when every other example is on a single spec line?

Why should a rule be created for one car? How would you write the spec lines? I am not for eliminating the VIN rule at this time but would be interested n how you would solve this 'problem' without messing with a class-wide rule...
[/b]
Easy, I would solve the problem by giving the Neon a single spec line in ITA.