Sounds like you should be looking for a cam in the 22x duration range, .500-.560 lift, you may want to check out Thunder Racing's line of cams. I really liked my 224-112 cam when I had it, it used basic Comp 918 springs, and provided a nice bump across the RPM band. A buddies full bolt-on 6 speed car made just over 400 to the wheels, and needed a set of injectors.
http://www.thunderracing.com/shop-by/vehicle/1998-2002-LS1-F-Body/Cylinder-Heads-and-Valvetrain/Camshafts/