318 steel crank or not?

I just bought a 1974 rebuilt 318 and was wondering how can you tell if it is a steel crank or not.It looks to me to have the thinner balancer on it which makes me think its a steel crank engine.I had a 73 340 years ago that had the wider balancer on it .So I always assumed the 340 was a cast crank motor.I know the general rule on a 383-440 is wide balancer is a cast crank engine.
Any ideas?I do have to change out the oil pan so is there anything to look for here that may help?

Thanks,Jim