Deck height of the Buick 350 small-block is taller than the deck height of the BBC, and by quite a bit.
OTOH, the bore center dimension is really small. The Buick 350 has a very small bore, and a very long stroke, which is "what they could do" with the Buick small-block architecture. Pontiac 350 is not as extreme as the Buick, but still a small-bore, long-stroke design.
The Olds 350 has the shortest stroke and biggest bore of all the old iron-block 350s.
OTOH, the bore center dimension is really small. The Buick 350 has a very small bore, and a very long stroke, which is "what they could do" with the Buick small-block architecture. Pontiac 350 is not as extreme as the Buick, but still a small-bore, long-stroke design.
The Olds 350 has the shortest stroke and biggest bore of all the old iron-block 350s.