Mostly everyone (including myself) is caught up with Shazam's achievement of such hp in the "smog motor" by stroking. Yes, he has a stroker motor, but we must remember there is some good horsepower in an efficent good breathing 408 CI engine. Based on Shazam's hp figures, he is a little over 1.8 hp per cubic inch. At 408, a good efficient engine can net 571.2 hp at just 1.4 hp per cubic inch. More than enough to stomp the majority of the Chevy drivers. The key is in the heads, intake, and cam selections. If you paid just $3,000 for the aluminum heads, and perhaps $500 for adapter plates and a strip dominator 351c intake you could pick up 100-150 hp easily over the well ported iron heads and most frequent used 400 performer intakes.You would have a better rod ratio, rod angularity, and a long life engine. I'm NOT knocking Shazam or his set up. It's just that most of us whom never experienced high horsepower have a tendency to throw horsepower numbers around effortlessly.400 hp is a lot. Once you start going over it, what are you'going to with it? Especially in a street driven vehicle.Do burn outs for the kids cause you can't get any traction? Track, racing, mudpulling, is fine. Beware of limited traction if your on the street.

Here are some dyno results from a 406 Ci in a pantera with iron heads.

RPM HP TQ
2000 158 415
2500 212 445
3000 274 480
3500 352 527
4000 431 566
4500 500 583
5000 543 571
5500 567 541
6000 577 505
6500 567 458

Here are the engine parts:
Ford 400 FMX block, bored .030", 4-bolt main
Stock rods/crank
Arias forged pistons
351C 4V heads, ported, 2.19/1.76 SS valves, 11:1 CR
Comp Pro Magnum 1.73 intake/1.8 exhaust roller rockers
Hall Pantera manifold
PME intake spacers
Weber 48 IDA's, 45mm chokes, Inglese needle/seats/circuits
Comp 32-771-8 Magnum roller cam
GTS Equal-length 2" headers"

 

I don't know what 800HP feels like, but I know about 500HP. There was never enough traction below 45mph in my '70 Fastback. I stated similar ideas in this thread I starter.

On the street, torque rules over HP.

Torque vs Horsepower refresher
http://www.fordmuscle.com/archives/2001/05/horsepower/