Try www.intense-racing.com they have 3800 fbodys running in the 8s. IMO, the supercharger, even with a cam, etc will probly only give you 300whp, powerdynes belt driven kits are sh!tty and max out at 12psi. If you serious about it i would reccommed going with a single t360-1 turbo or something, then your 400whp goal can be achieved. You wont hit 400whp in a 3800 camaro with a powerdyne..
Give them a call and you can go as fast as you need to as long as you have the chee$e.