A (forged) 340 Crank is Not a (forged) 273/318 Crank?

Just read on another forum that a 340 forged crank has "lightening" holes drilled in the #1 and #4 rod pin areas, the 273/318 forged crank does not. Never heard that before. I wonder if that is universally true for identifying the Mopar factory forged crankshafts?