The 2001 Mustangs have the following spec's;
Base 3.8L
193 HP @ 5,500 RPM
225 LB @ 2,800 RPM
4.6L SOHC GT
260 HP @ 5,250 RPM
302 LB @ 4,600 RPM
Cobra
320 HP @ 6,000 RPM
317 LB @ 4,750 RPM
Of course that is factory 'net flywheel' horse power, not RWHP.
To get your RWHP rating you would have to deduct about 20%
for automatic cars, and around 15% for 5 speeds..