The fully assembled Dart Pro 1 heads are made from strong 355-T6 aluminum and feature a big 2.250-inch intake and 1.880-inch exhaust valves. Twedt did do a mild amount of porting to the cross-section and short turn radius. The key was to do just enough to improve flow and cylinder fill, but not slow down the airspeed at low to mid-lift point. He also performed a five-angle radius valve job. The heads were then secured using an ARP stud kit and sealed with a Fel-Pro gasket (PN 1047, $46).