No freeze plugs on an aluminum S6. I’ve hade several motors. One of which I rebuilt. Pretty unique motor. The heads are cast iron and unique to the aluminum block. Has todo with the unique water passages. As far as getting parts, it’s a Challange. Hard part was getting a rebuild kit. All that was available at the time was from Kanter. There’s a FABO member that races those motors. I sold him a complete motor years ago.