When I was at Speedweek in 2011, I saw George drive a couple of different cars going for records. He had "Speed Demon" out as well as "Blowfish" (turbo'd 'Cuda)
So far (I have seen a reference to) Speed Demon exiting the flying mile at 460 something (and eating its transmission alive in the process)
They run that car with several different SBC engines - the "baby" one being just over 300 inches and the big one at 360 some. When I saw it, they had the 347 in it.
They also run it with a blown 4 cyl Mopar in it