I'm not running your typical fuel system since I have a fuel cell and aeromotive fuel system components.
However, most everyone else I Know who run these are making 600-700rwhp with twin 255s with larger rails and lines. On stock fuel lines and rails you can make up to 600-650rwhp but may run into fueling issues when you get close to that 650 mark. When talking about ET, I have friends who are running 10.6 in the 1/4 with these.