My understanding is it was no problem making big cube small blocks with the right blocks etc, but. A huge difference is in the heads. A big block head can simply flow that much more air than a small block. And appart from the actual extra cost of BB blocks and heads, if you are really making big horse power small blocks and spending the $$ you will probably always spend more on the SB than the BB for the same amount of power. Just look at the crate motors you can buy from companies such as World. look at the prices for a similar HP and cubed small and big block, BB is cheaper. And you probably got a fatter torque curve too......
Big Blocks RULE.... simple as that;46