If it has the full depth hole for a pilot bushing it's forged. I have yet to find a BB cast crank with a pilot bushing hole that was drilled to depth. I even took a 400 out of a 75 pickup that had a 4 spd and it was a forged crank. Not saying they aren't out there, but I've looked at a lot of crankshafts and I haven't seen one yet.
Also, if you get the pan off and look the counterweights over good, the cast will look very nice and squared. The forging is rather an ugly piece. And a cast 440 crank will have 440 cast into it on one of the counterweights.
One more thing, unless it's been previously balanced or has six pack rods, it'll be internally balanced.