... Actually you don't need the "Helcat" (*corr: "Hellcat") to be competitive with the new Mustang. The 485 HP HEMI will probably run away from the Mustang with the new 8 speed Torque-flight transmission.
The standard 33k base price 2015 Mustang GT is not made to compete against the 47k base price 2015 SRT 392, that will be the job of the GT350/GT500 variant ...
Most recent real world 1/4 mile testing ...
"Hellcat to 60 mph in 3.6 seconds—0.1 behind the GT500
—and through the quarter-mile in 11.7 at 126 mph—0.1-second ahead and 1-mph faster than the GT500. Dodge quotes an 11.2-second quarter-mile on the tacky surface of an NHRA-certified drag strip
, but the Pirellis feel so overstressed that hitting that low ET would also require dropping tire pressures to about 10 psi
. (We always conduct our acceleration tests at the manufacturer’s recommended tire pressures
.)" 2015 Dodge Challenger SRT Hellcat Test – Review – Car and Driver