Streets and Bowtiegirl are correct. Buick, Pontiac, Olds, And Cad (rear-wheel drive) all have the same bellhousing bolt pattern. Chevrolet is different. Front engine-to-frame mounts may or may not be the same depending on year & application.

Matt167 is a little off base. The difference in horsepower & torque in two engines of the same configuration is not a difference in bore & stroke, but comes from a difference in the cam, heads, and induction system. All stock Chevy 350's, for instance, came with a 4.00" bore and 3.48" stroke, but horsepower ranged from 165 to 375+.