440 RB stock Pistons
The arrow on the piston [ or could be dimple or notch ] goes to the front of the engine. There are 4 left & 4 right. Now look at the big end of the rod, where the bearing shells fit. One side of the rod has a noticeable chamfer, the other side does not. The chamfered side goes against the crank cheek....with the arrow on the piston pointing forward.