Off-road x-pipe, magnaflow cat back, 70mm throttle body, CAI, pulleys, and tuned chip on dyno. Resulted in 258 rwhp. ( / .85) = about 303 hp at the flywheel, pretty close to the 2010 GT, and your car has a 335lb weight advantage. I had 3.73's and drag radials and could manage consistent low 13 1/4 mile times.
OR, Above exhaust, CAI and throttle body + Kenne Bell blower @ 8psi = 440 hp at the flywheel. Smokes stock 03/04 cobras.
2000 Mustang GT Spec Ed.
1.7L Non-IC Kenne Bell Supercharger
70mm FRPP Throttle Body
3.73 gears, CAI
King Cobra Clutch
375rwhp w/ 8psi
1/4 mile - 12.50 @ 113.5mph