What is a bore bore blower? or did you mean Big Bore blower?
The KB 2.6 was available for order 2 weeks ago. In fact there's a guy at the salt flats right now running his Cobra with one in an attempt to set a new lan speed record for a production supercharged vehicle. KB has also released a 2.8 blower! These new blowers use a new screw design which is supposed to be more efficient than their previous 2.2 & 2.4 liter models.
Whipple has a 3.3 blower, but I don't think it's been released for use on the Cobra yet.