Here's my combo...
435" 385 series ford based build, 7.88:1 compression.
Custom Vortech V7-JT supercharger setup (my design)
EFI (my design, built on OEM Ford EEC-IV)
Viper 6spd
All under-hood, no bubbles, hickeys, etc are required.
So far I've spun the engine to 5500rpm and here's what I've learned.
500ft-lbs of torque at 2500rpm, 660ft-lbs of torque at 5500rpm, 660hp at 5500rpm and climbing straight up at shut down. Peak torque occurs at 5600rpm, meaning peak power will be somewhere up around 6500-7000. These are rear wheel chassis dyno figures and were produced on a dynojet 248 running only 16deg total advance and 11:1 AFR. I'm purposely leaving it soft for the break-in miles; there's probably another 50-100hp in there if I simply add spark, but all of them are useless...I'm beyond the traction limit now.
After break-in miles (the WSCB), I'll check the lash and go ahead and spin it to 7K and see what she makes. 800rwhp probably, as pulleyed, with the potential for 30% more boost.
I don't know why you'd want more torque or more power in a cobra, and my car is a heavy example weighing in at 3000lbs (West Coast). The car easily breaks traction in 4th gear starting at freeway speeds with 335's in the rear. Drop 500lbs and it would be even worse.
There's pictures in my gallery, and here's a video taken last weekend.
http://www.youtube.com/watch?v=17qAk_LIN8U
Now, if you're building something with short stroke, then I could see it...stock 302 with a Whipple and 5psi would be enough for one of these cars. If you have a specific goal in mind, maybe you need more. My goal is 1000fwhp; which means I want 800 at the rear wheels. Why? Why not, makes me happy.
Oh, and as far as centrifugals go, all I can really recommend is to stay away from ball drives. I've owned a few of them, and they leave me wanting. The boost is variable depending on how hot the
oil gets. If you drive the car hard, slip will occur and you'll fry the ball drive. I've had a belt-drive (powerdyne) unit too, and though I was able to get away with road-race and other abuse, others were far from as lucky. Go with a gear drive unit. I prefer Vortech, but opinions vary. And whatever you get, make sure it includes a bypass valve for part-throttle venting of all that hot air during cruise.