Stroke a 318

If you are going with a CNC kit, pay for them to balance, especially if you are going to use the cast crank. You might get lucky if you opt for the diamond pistons as another member suggested with the cast crank, because they are much lighter than the icon pistons, but I doubt it.
If doing it piecemeal, I would recommend paying more for the forged crank, not due to any weakness of the Scat 9000 cast, but because it is much cheaper to remove metal when balancing than to have heavy metal added