You can make 500 +HP (+ or - 3 to 6 HP) with a set of mildly ported 906 heads with a decent set of 2,14 intake valves and 1.81 exhaust valves with 9.5 to 1 comp ratio and a 850 CFM or bigger Holley or other decent Holley type 4150 type carb. double pumper carb. and a decent hydraulic lifter cam with 260 + degrees at .050 on either 108 or 110 LSA installed at 2 to 6 degrees advanced on the intake lobes