If your donor engine hasn't been damaged from overheating or detonation, it's likely that both the crank and connecting rods are reusable along with the block and heads. Still, it's a good idea to clip the caps and resize them (shown here). This process ensures that the rods are nice and round. Otherwise, it will squeeze the rod bearing against the crank journal. This can cause the bearing to shed layers, putting metal into the system, and eventually spin a bearing.