Balance question

Chrysler never made a cast crank that is internally balanced. They're all externally balanced. They did make a lot of 318 cranks that were internally balanced though. They were all forged.
Anytime you change a piston or connecting rod the engine (crank, rods, and pistons) MUST get rebalanced. The only time you can get away with it is if you are using stock rods and replacement cast pistons. The weights are close enough for a street car. No one uses cast pistons in a race car.

don