What is that piston, flat top with no valve reliefs, six pak piston with four valve reliefs or the high compression piston with the small dome? If they are the small dome high compression pistons be very careful on how much compression the motor will have with the iron heads I have built a lot of stock stroke 440 motors with iron heads, both open and close chamber heads, 9.6 to 1 is the most I'll use on the compression ratio for a pump gas motor BTW, 500 HP and 540 + ft. lbs torque is not hard to make with a stock stroke, 9.5 to 1 comp. ratio iron headed 440