Hi Southernman. Allpar is one source of confusion that started all this mess. I don't know who wrote that site but it has it's share of error's, one being the 318 was externally balanced. A cast vs. a steel crank is not what determines if an engine will be externally or internally balanced although cast cranks are lighter so sometimes (as in the case of a 360) they don't have enough weight on the counterweights to balance the reciprocating assy.
I understand it's not a problem swapping parts as long as they are matched (internal vs. external balance).
Thanks for the feedback.