[BCreekDave]

Maybe there is a bit more to this, I'm not sure.
I base this on the 1970 Camaro Supplement to the Chassis service and Overhaul Manual, page 13 in the Specifications section. Section 9 the Standard and Power steering specifications.

The "Gear Ratio" specs for the 6 cylinder and the Z-28 (and maybe the stand-alone F-41 option?) are both listed at 24:1. When you look at the overall it changes from 28.3:1 for the 6 cylinder to 22.3:1 for Z-28. To me, the only way this change could happen would be beyond the steering box and to the linkage. This would happen then with a longer arm on the Z-28. The longer arm would move the linkage farther for a given rotation of the box input shaft.

Other V-8's list a different box ratio of 28:1 and a still different 33.1:1 overall ratio. If you do the math, the 6 cylinder and the other V-8's have the same offset from the box ratio to the overall ratio at 0.84:1, meaning that the pitman arms are probably the same.

So, I think there are two different pitman arm lengths and 2 different box ratios for manual steering Camaros in 1970.