First I'd like to confirm that a 1972 would have come with a "Small" [1-1/8"] sector shaft, correct? Across the splines on my original box is about 0.030" over 1.125", which makes me ask the question.

Secondly, assuming I had a small sector shaft car, what would it take to upgrade it to the larger 1-1/4"? Is it simply the right box and associated pitman arm from a '73+ Ebody?

Going with the idea that bigger is better with this component.