So I just watched the 04 mustang shoot out in the video section, and it shows a stock mach 1 in his first 1/4 mile run a 13.15 with regular tires. That time is better then everyone who has posted in the 1/4 miles runs and thats including mods on our cars,(bolt ons)  I have 18in stock tires, cowl hood, under drive pulleys, cold air kit, predetor tune, 3.73 gears and flowmaster mufflers, my best time before the gears were changed  was a 13.55.  THe mach 1's don't have over 300 hp do they? HOw are they faster?  

The mach one is a DOHC aluminum engine with 305 hp and 320 lb.ft. with a factory curb weight of 3,450 lbs with 3.55 gears

The 05 Gt is a SOHC three valve aluminum with 305 hp and 320 lb.ft. and a factory curb weight of 3,450 lbs and 3.55 gears (w/ manual trans)

So basically you are looking at driver skill, temperature and elevation if your car and the mach are both manuals.  

I just bought a 03 mach 1 and the factory number is 305 hp but they say that that is low.  

The Mach one was rated @ 335 ft-lbs torque and has a higher rev limit,which allows a third gear 1/4 mile
through the lights. The 05-present GT has too shift into 4th gear. This small difference comes into play in controlled conditions like a drag strip.Mach I ratings;Horsepower: 310 @ 6,000 rpm
Torque : 335 ft-lb @ 4,200 rpm
Mustang GT ;Horsepower 300 @ 6,000 rpm  
Torque 315 lb-ft @ 4,500 rpm  

Man i hate to break it to you but even a 5.0 can beat one of the new S197's. Trust me all i have on my 85 5.0 is a full exhaust, underdrive pulleys, BBK Cold Air box and a short throw and i gave it a run for its money. I do believe it all relates to how much the S197's weight, i think 3450 lbs. seems a little low for that car to be honest with you.  

Probably is low, factory weight ratings tend to be lower than the actual weight people see but that is why I gave the factory rating for both cars.  It was just to show that the cars are about on an even playing field.  
AS for blueoval nut, I will say that the higher rpm redline is true (6,800) as long as it is a manual.  The automatic has a cast instead of forged crank and has a lower redline (stupid I know, I found out from a guy who bought an auto and then found out this little detail).  But the guy who started this post didn't say weither the car he watched was a manual or not.  

sorry in the video the guy was driving a stick. If you want to see the video just go to the video section on this sight and look at the one that says 04 mach 1 mustang shootout  

Mach 1 has more power and is lighter, not to mention that POS 2 piece driveshaft the s197 has robbs it of about 2 tenths off the bat until you change it.  

The latest MM&FF had a shoot-out of 7 cars all running naturally aspirated engines.  It showed the 01 Stangs weighing between 3100 and 3200 lbs.  S197s weigh at least 3450 and probably over 3500 lbs.  That's a lot of weight difference which surely accounts for the better ETs on the earlier Stangs.