It is because the Big Block engine frame mounts move the engine slightly to the pass side. The reason is, the drivers exhaust manifold would either hit or would be too close to the steering box. So with the engine being shifted to the pass side they had to also offset the transmission cross member. Because of that, to get the shifter handle to sit centered in the hole, they had a different shifter bracket for B/B. To compensate for that they needed shifter rods that were angled differently.
- Warren