Need some info - "318-3" engine

Generally -3 motors were truck/industrial/marine engines. Many had the same heavy duty goodies inside as the hi-po engines of the same year. That being said, I think the forged 3.31 stroke cranks were all used up by 73 (even the 340 went to cast).

There should be a VIN stanped on the pan rail to confirm what it was in originally.

Also, the -3 designation should be stamped in on the left front as well.