When are you too large for an early A body....

I agree 66-70 B is a better driving position than 71-74 B or E.

However, 67-76 A is very close to 66-70 B, especially "29" bodies.

Ratio of interior room to "compact" exterior is way better in a Duster/Demon/Dart Sport.

As far a C body cars go- they are wider and longer but don't have any more headroom than my favorites listed above.