Plenty of people have just installed the new forged parts without balancing and had it work fine. Our crank is some what balanced from the factory. The damper is balanced, and the flywheel/flexplate is balanced. So in theory, if you install a rod/piston combination across all 6 holes that are very close in gram weight, then you will be within a close percentage of being in a passable balance.
You match lighter pistons from the group, to heavy rods from the group, to try to make all 6 rod/piston combinations close to the same gram weight.
Now all that being said, you could get away with not machine balancing your rotating assembly, but why? It is not a high cost to spin balalance the entire assembly. For any higher HP car, I mandate that the entire rotating assembley be high speed spin balanced to under 1 gram accross 3 points of the crank.
To do a high speed spin balance, you need: The finished crank, the damper, the flywheel/flexplate, the flywheel bolts. Also, you will need the weight in grams of: each piston with the pin and rings, Each rod with its bearing installed. You could just give the piston and rod assembly to the machinist to gram scale, but if you don't want to mail all of that stuff, just gram scale it yourself.