IF YOU WANT THE ULTIMATE PRO MOD ENGINE, THIS 903 IS THE ANSWER, FEATURES SONNY'S PRO MOD "GM" 16 DEGREE STAGE 2 CYLINDER HEADS, BILLET CN BLOCK, GRP RODS, 70MM CAMSHAFT, THIS ENGINE MAKES OVER 1740 HP NATURALLY ASPIRATED AND OVER 2850 HP ON FOUR systems