When JB hit his tee shot 359 in the playoff at the FBR, the announcers saud his clubhead speed, measured by Shotlink, was 139 mph.
At 109 mph, the modern ball goes about 290 yards.
Add 2-3 yard per mph, and the modern ball goes 60 to 90 yards farther at 139, for a total of 350-380 yards.
Seems the talent required to move the clubhead at 139 mph trumps improvements in ball technology when it comes to producing prodigeous drives.