Yes. They are different.
The 71 and 72 Chevelle steering wheels had a single, very wide, horizontal crossmember. It was thicker at the center than it was at each side where it contacted the outer ring of the steering wheel itself. Maybe about 2 inches at the ends and 4 inches in the middle.
So, basically the crossmember is shaped like a very flat triangle with the left and right sides chopped off. The entire thing is covered with a rubber cover, which can be pushed just about anywhere to blow the horn. The rubber cover also has a metal insert that runs across the entire width of the crossmember. On a stock Chevelle, the insert has the word Chevelle printed on it on the right side. On a stock SS Chevelle, the insert has a small, slightly raised, SS in the center. The insert is usually black with a silver outer edge, and the letters are silver.
It is a very plain looking steering wheel, but it is great for driving. I drove my 72 SS with its stock steering wheel for 12 years and found it to be one of the most comfortable I've ever used.
Hope that helps. If I still had a picture, I would have tried to send it to you.
Bob