Crane Gold rocker mystery??

The balancers are 7.25 IIRC in diameter, making the perimeter 22.7766 inches and 90* would be 1/4 of that so 5.69 inches. I'm thinking you are on the right track, easy fix for sure.

As for the pinion, it has to be nose down relative to the the driveshaft. The driveshaft itself should be going downhill from the trans. This makes the two U-joints cycle in opposite directions and so if they were equal angles the vibration would cancel.
However, they cannot be equal and opposite under all conditions.The major compensation is for axle-wrap under power. This changes with the amount of power,the body weight, and with the stiffness of the springs. With lots of power and a single factory main leaf, you might need 7 degrees nose down, to prevent over-rotation of the rear end. Less power, and less traction, requires less compensation.
Cruising requires the least front to rear difference, for smooth sailing. Ideally they would be equal and opposite, perhaps 1.5 to 2 degrees. But if your power wraps the rear up from 1.5 to 2* nose down to 5* nose up, well, you cant have that! So cruising has to be sacrificed, or the springs have to be stiffer.
Ideally the rear angle will be slightly nose down under full power.