How do u get that number when stock mustangs have about 300 horse
UMMM, no. The 'stang 5.0l had anywhere betwwen 225 and 205. The engines are all basically the same, the difference was was the way they tested. Up to 92 (225 hp) they tested just the engine. 93+ was tested with all accessories on the engine.
My '94 Cobra, when it was mostly stock: (full exhaust only)
275 HP at the crank. (Ford said 240, you cant trust them.)
Cast iron GT40 heads
Cast aluminum Cobra intake manifold
Crane 1.7 rocker arms
24lb fuel injectors
Cobra specific ECU (computer)
"Cobra" stamped valve covers with build sticker and signature
Engine oil cooler
Front mounted power steering fluid cooler
Lightened flywheel
Phosphate coated transmission gears
Cobra specific underdrive pulleys
Cobra specific camshaft
Edit: I wouldnt even think about building over 400 HP from a factory block. They will split in half!! It may hold up for a while, but be forewarned.