426 was just a bigger bore 413. the cam was rated at 268 degrees duration, .430 lift, 110lsa. no adjustable rockers and the hydraulic tappets should not be easy to depress. the 750 edelbrock is the same size as a '67 375hp 440. I would use the 440 factory jetting with the edlebrock carb and factory style intake. all the 750 edelbrocks I have came with .113 primary jets and .095 secondary jets. i would step the primaries down to .104 and the secondaries to .089. a fat fuel curve will definitely take power out of the engine, but the factory engines only made about 305hp. they were more of a torque engine than horsepower.