340 with metal in oil pan

I don’t know the history on the motor I just bought the car a little over a year ago and haven’t had time to really drive it much it started making a slight knock so I stop driving it pulled the engine and found the metal. After I left this post I pulled the heads and somebody put one of my pistons in 180° the wrong way and the valves have been tapping the piston I am believing this would explain my debris ending up in the oil pan?