Bore vs Stroke
Pontiacs have a longer stroke. On a 350 the stroke is 3.75 vs 3.48 for the chevy. Wilder cam would be multiplied by the difference in stroke. eg, filling the cylinder more.
Pontiacs are notorious for good torque but not as high revving compared to chevy.
6200-6500 RPM on a street Pontiac is screaming.
That's my theory on your question.