need to learn about camshafts....

run what's in it and add 1.72 roller rockers - to calculate gross cam lift you multiply the cam lobe lift by 1.5, 1.6, 1.72, ect... Magnums come with 1.6's IIRC.. just be sure to rotate the motor over by hand 4 revolutions slowly to make sure the valves clear the pistons..