The main difference I always thought between SB and BB was that SB can give a great performance engine with good weight advantage but it would be quite stressed. A BB could be made to make the some power without as much stress but it is heavier, bulkier etc.
If I was to do a lot of track time I would prefer a SB but for general crusing with lots of noise (Which is what I do
) I prefer my BB. It all depends on what you want out of your Cobra.
Of course, I could be completly wrong about all of this
and have no idea what I'm talking about
Paul