I've seen a bunch of pre '71 318s that were forged cranks. You cant tell by the balancers like the big block. The only way I know of for sure is to take the oil pan off and look.
That's exactly right.....I have been pulling pans off every 318 I have found looking for a forged piece. But what the early 318 blocks are really good for is a good amount of them can be bored to 4".......they are a thick wall casting but the only way to know for sure is to sonic check them. Truck and boat motors usually have the best chance. '67 - 70 are the best odds to find them too......