Hot Rod magazine built a cast crank 340 using the 318-3 cast crank years back, so the cast cranks can be interchanged. The reasoning was that the 318-3 crank was primarily a truck crank and was supposedly stronger.
Correct me if I am wrong but as far as I knew a 318-3 was a heavy duty truck motor and had a steel crank in it and fully floating rods as well as other strength parts.
