The best way to build that "Windsor style" 427 is to start with the Dart or Ford Racing new Boss Windsor block and have the 4.125 bore with the 4.00 stroke. With this you get a much stronger splayed 4 bolt block designed for 427 cubes to start with.
My build going on 7 yrs. of use now used the same heads and was in the 550 HP area with milder 242/249 hyd. roller.
Well it did run high 10's at 132 in my little '85 Mustang with 3.50 gear.