The interesting thing about all that is that Pontiac kept the same stroke for the 326, 350 (354), 389 and the 400 (3.75" stroke).
When Chevy went from 350 to 400 cubic inches on their small block, they changed both bore and stroke. The 350 Chevy has a short 3.48" stroke, so the 350 Pontiac actually made more torque.
When the Chevy guys want to get torque (and horsepower) out of their 350s, they install a Chevy 400 crank to get 383 cubic inches. The Chevy 400 crank has a 3.75" stroke.... just like the Pontiac. The Chevy guys, in building thier 383s, are building an engine with almost the exact same bore & stroke as an old Pontiac 389. (389 is 4.063 x 3.75, and the 383 Chevy is 4.030 x 3.75) The small block Chevy 400 has the exact same bore & stroke as the 400 Pontiac (4.12 x 3.75), and that's the hot ticket for a small block...