Maybe......but considering how many root screw options there are for the 03-04 Cobra its unlikely. Look at it like this: the GT 500 comes stock with a 2.1. So it has 2 upgrade options, the 3.4 and 2.9. The Cobra has 2 upgrade options, the 2.3 and 3.4. I think the 2.9 would be redundant and cut into the 3.4 sales. But I think on a 4.6 the 2.9 would make more sense than a 3.4. Just my .02. And then there are the Kenne Bell blower options...............
My tuner has had one on his Lightning for quite some time now. He makes pretty insane power for the mods he has being just a built block and full exhaust (680/650 IIRC) with only 12˚ of total timing (boost, not sure on). It is definitely a pretty slick unit all installed and pretty looking. From what he told me, the 3.4L is more of a race driven blower that runs much more efficiently at 19+psi of boost whereas the new 2.9L blower will be much more efficient from the 15psi-20psi range (where most people keep their blowers at) while creating a nice power curve.