I believe you are too small on the intake runner unless you will turn some huge RPM. Remember, the engine is nothing but an air pump.
One of my engines is the same if you are 4.625 x 4.625 We elected not to go with Big Dukes because we already had the Chevy pattern pistons. We have the Brodix BB-3 which have 370cc intake port and the exhaust valve is moved over .030
JMO.