[KrAzEcJ]

Not to sure of your question without a little background info. You wrote new 427, what machine work has been done to the block? Anyway need a little more info to try and help. If the block has been machined and you have the old pistons that came with the motor most likely they are now to small. If you havent had any machine work done at all you need to have the block checked out by a reputable machine shop and once its checked out you will know how each cylinder bore is and wether it has to be bored 20, 30, 40 etc.... to get the bores in good shape and alligned. Then you will know about piston size. As far as rods have them tested and sized. When you get a chance post some more information.