LA vs Magnum crankshaft

When you get a new crankshaft it will have to be balanced in most cases. Where are you finding these crankshafts?

When the connecting rods are lighter, as is the case in the magnum, it throws the bobweight off. The bobweight is what determines how much material is drilled or added to the crankshaft counterweights to balance the engine. Magnum rods and pistons are different from LA rods and pistons, therefore the bobweights are different. Now, you can put LA rods and pistons in a magnum, or you can put magnum rods and pistons on an LA crankshaft. But in either case, to do it right would require a rebalance.

The pilot bushing issue will be determined if you are running an automatic or manual transmission.