Which Slant 6 to build?

Is there a way to confirm cast crank? I do have easy access to that as the oil pan is off. The guy gave me a car oil pan to go with it. Cherry picker and engine stand are on my wish list. I too was thinking to build the 81 due to hardened seats and hydrolic lifters. Just wanted to see if there was anything that would stand out as an issue or benefit of going with a late model motor.