what rods would be better for my build

A forging process starts with a piece of solid material (typically steel or aluminum), it may just be a piece of bar stock or could be a roughly shaped to match the final shape. With steel the piece of stock is normally heated up until it's red hot (actual temperature will be dependent on alloy) aluminum is forged at room temperature most often.

Back in the day when I was visiting our forging suppliers they had three stage dies built into one forging press. The piece of material would be hit by the press in each die 3-5 times. You can actually hear when the part is not being formed any longer when the noise goes from a dull thud to a sharp bang then would move to the next stage. The last step before the part was quenched was another die set that trimmed off the flash. This is why you can id a forged crank from a cast crank, the area where the excess metal is trimmed is very wide compared to a small parting line in a casting die.

FWIW, a forged crank is forged with all the rod throws in the same plane. It is then twisted to get them offset by 90 degrees.

The defects in the table above are real issues that any outfit that forges or casts material has to deal with.