You can check out my build on:
www.2gmotorsports.com under dart 427. The engine was built by Keith Craft and dynoed by them. The engine made 615 HP at 5600 RPM and 619 ft-lb at 4600 RPM using 1 5/8" primaries (same as I currently have for the GT40). The engine really could use 1 7/8" primaries however I have not had a custom set made for the GT40 (but will). Nice combo using hyd-roller cam and 10.5:1 (pump gas). The AFR's are hard to beat.